[Google Pixel 2 XL Questions & Answers] ScottIsMyName:
I thought about this as well but then I thought that dding the boot partition would require root.

edit: decided to try it, and it looks like root is indeed required:

taimen:/dev/block/platform/soc/1da4000.ufshc/by-name $ ls -la
total 0
drwxr-xr-x 2 root root 1280 1970-01-21 18:16 .
drwxr-xr-x 4 root root 1460 1970-01-21 18:16 ..
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 abl_a -> /dev/block/sde6
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 abl_b -> /dev/block/sde20
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 aes_a -> /dev/block/sda10
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 aes_b -> /dev/block/sda11
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 align_parti -> /dev/block/sda12
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 apdp -> /dev/block/sde29
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 boot_a -> /dev/block/sde8
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 boot_b -> /dev/block/sde22
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 cdt -> /dev/block/sdd1
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 cmnlib64_a -> /dev/block/sde10
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 cmnlib64_b -> /dev/block/sde24
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 cmnlib_a -> /dev/block/sde9
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 cmnlib_b -> /dev/block/sde23
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 ddr -> /dev/block/sdd2
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 devcfg_a -> /dev/block/sde11
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 devcfg_b -> /dev/block/sde25
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 devinfo -> /dev/block/sde34
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 dip -> /dev/block/sde35
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 dpo -> /dev/block/sde36
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 dtbo_a -> /dev/block/sde13
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 dtbo_b -> /dev/block/sde27
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 frp -> /dev/block/sdg1
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 fsc -> /dev/block/sdf3
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 fsg -> /dev/block/sde32
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 ftm -> /dev/block/sda6
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 hyp_a -> /dev/block/sde3
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 hyp_b -> /dev/block/sde17
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 keymaster_a -> /dev/block/sde7
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 keymaster_b -> /dev/block/sde21
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 laf_a -> /dev/block/sda1
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 laf_b -> /dev/block/sda2
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 limits -> /dev/block/sde37
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 logfs -> /dev/block/sde39
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 metadata -> /dev/block/sde41
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 misc -> /dev/block/sda5
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 modem_a -> /dev/block/sde5
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 modem_b -> /dev/block/sde19
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 modemst1 -> /dev/block/sdf1
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 modemst2 -> /dev/block/sdf2
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 msadp -> /dev/block/sde30
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 persist -> /dev/block/sda4
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 pmic_a -> /dev/block/sde4
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 pmic_b -> /dev/block/sde18
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 pstore -> /dev/block/sda9
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 rpm_a -> /dev/block/sde1
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 rpm_b -> /dev/block/sde15
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 sec -> /dev/block/sde33
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 ssd -> /dev/block/sda3
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 sti -> /dev/block/sde40
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 storsec -> /dev/block/sde31
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 system_a -> /dev/block/sda7
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 system_b -> /dev/block/sda8
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 toolsfv -> /dev/block/sde38
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 tz_a -> /dev/block/sde2
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 tz_b -> /dev/block/sde16
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 userdata -> /dev/block/sda13
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 vbmeta_a -> /dev/block/sde12
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 vbmeta_b -> /dev/block/sde26
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 vendor_a -> /dev/block/sde14
lrwxrwxrwx 1 root root 16 1970-01-21 18:16 vendor_b -> /dev/block/sde28
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 xbl_a -> /dev/block/sdb1
lrwxrwxrwx 1 root root 15 1970-01-21 18:16 xbl_b -> /dev/block/sdc1
taimen:/dev/block/platform/soc/1da4000.ufshc/by-name $ dd if=/dev/block/sde8 of=/sdcard/boot.img
dd: /dev/block/sde8: Permission denied