[OnePlus 3 & 3T Cross Device Development] Doc Sniper:
Changes between versions 3.1.1-0 and 3.1.1-1 were made (only) to the ramdisk, see Checksums:

$ sha256sum twrp-3.3.1-0-oneplus3.img

4a850520d18b9b2669734841e4a483ccf6ede64799b7d10c0ad7907511d8e896 devicetree.dtb
a5442a3a8b0f0837dedbc05b7751fb17c85dff8f7fa93a072173d92432a27430 kernel
33bd635bf7e63951d8fe042472955be355d500333781f902a5471a6949df174a kernelimage
1e9c98dd7407c94c0936671dacd5975da3a0607051f40b8ab76f6e688d158c35 ramdisk

$ sha256sum twrp-3.3.1-1-oneplus3.img

4a850520d18b9b2669734841e4a483ccf6ede64799b7d10c0ad7907511d8e896 devicetree.dtb
a5442a3a8b0f0837dedbc05b7751fb17c85dff8f7fa93a072173d92432a27430 kernel
33bd635bf7e63951d8fe042472955be355d500333781f902a5471a6949df174a kernelimage
019edfb2dcedc28d2d2689354c17a0a1a49bc64fc865dc84f9125f29b5c6c8c6 ramdisk

Here the changed/removed/added files in detail:

Files TWRP3310/default.prop and TWRP3311/default.prop differ
Files TWRP3310/file_contexts.bin and TWRP3311/file_contexts.bin differ
Files TWRP3310/init and TWRP3311/init differ
Files TWRP3310/init.rc and TWRP3311/init.rc differ
Only in TWRP3311: init.recovery.ldconfig.rc
Files TWRP3310/prop.default and TWRP3311/prop.default differ
Files TWRP3310/sbin/adbd and TWRP3311/sbin/adbd differ
Only in TWRP3311/sbin: [email]android.hardware.confirmationui@1.0.so[/email]
Files TWRP3310/sbin/android.hardware.gatekeeper@1.0.so and TWRP3311/sbin/android.hardware.gatekeeper@1.0.so differ
Files TWRP3310/sbin/android.hardware.keymaster@3.0.so and TWRP3311/sbin/android.hardware.keymaster@3.0.so differ
Files TWRP3310/sbin/android.hardware.keymaster@4.0.so and TWRP3311/sbin/android.hardware.keymaster@4.0.so differ
Files TWRP3310/sbin/android.hardware.weaver@1.0.so and TWRP3311/sbin/android.hardware.weaver@1.0.so differ
Files TWRP3310/sbin/android.hidl.token@1.0.so and TWRP3311/sbin/android.hidl.token@1.0.so differ
Files TWRP3310/sbin/android.system.wifi.keystore@1.0.so and TWRP3311/sbin/android.system.wifi.keystore@1.0.so differ
Files TWRP3310/sbin/avbctl and TWRP3311/sbin/avbctl differ
Files TWRP3310/sbin/charger and TWRP3311/sbin/charger differ
Files TWRP3310/sbin/hwservicemanager and TWRP3311/sbin/hwservicemanager differ
Files TWRP3310/sbin/keystore and TWRP3311/sbin/keystore differ
Files TWRP3310/sbin/keystore_auth and TWRP3311/sbin/keystore_auth differ
Files TWRP3310/sbin/keystore_cli and TWRP3311/sbin/keystore_cli differ
Only in TWRP3311/sbin: ld.config.txt
Files TWRP3310/sbin/libaosprecovery.so and TWRP3311/sbin/libaosprecovery.so differ
Files TWRP3310/sbin/libbinder.so and TWRP3311/sbin/libbinder.so differ
Files TWRP3310/sbin/libcryptfsfde.so and TWRP3311/sbin/libcryptfsfde.so differ
Files TWRP3310/sbin/libe4crypt.so and TWRP3311/sbin/libe4crypt.so differ
Files TWRP3310/sbin/libgatekeeper.so and TWRP3311/sbin/libgatekeeper.so differ
Files TWRP3310/sbin/libhidlbase.so and TWRP3311/sbin/libhidlbase.so differ
Files TWRP3310/sbin/libhidltransport.so and TWRP3311/sbin/libhidltransport.so differ
Files TWRP3310/sbin/libhwbinder.so and TWRP3311/sbin/libhwbinder.so differ
Files TWRP3310/sbin/libkeymaster4support.so and TWRP3311/sbin/libkeymaster4support.so differ
Files TWRP3310/sbin/libkeystore_aidl.so and TWRP3311/sbin/libkeystore_aidl.so differ
Files TWRP3310/sbin/libkeystore_binder.so and TWRP3311/sbin/libkeystore_binder.so differ
Files TWRP3310/sbin/libkeystore_parcelables.so and TWRP3311/sbin/libkeystore_parcelables.so differ
Files TWRP3310/sbin/libminadbd.so and TWRP3311/sbin/libminadbd.so differ
Files TWRP3310/sbin/libwifikeystorehal.so and TWRP3311/sbin/libwifikeystorehal.so differ
Files TWRP3310/sbin/recovery and TWRP3311/sbin/recovery differ
Files TWRP3310/sbin/twrp and TWRP3311/sbin/twrp differ
Files TWRP3310/sbin/ueventd and TWRP3311/sbin/ueventd differ
Files TWRP3310/sbin/watchdogd and TWRP3311/sbin/watchdogd differ
Files TWRP3310/sepolicy and TWRP3311/sepolicy differ
Files TWRP3310/twres/languages/pt_PT.xml and TWRP3311/twres/languages/pt_PT.xml differ