I am not sure if I got your point.
By using emulator, we can see below messages.

// No argument case which is similar to "gsm signal" command. 
gsm lte_signal
KO: not enough arguments: see 'help gsm lte_signal' for details

// Helper which is also similar to "help gsm signal"
help gsm lte_signal
'gsm lte_signal <rxlev> <rsrp> <rssnr>' changes the reported LTE rxlev, rsrp and rssnr.
rxlev range is 0..63 and 99 for unknown
rsrp range is 44..140 dBm and 65535 for invalid
rssnr range is -200..300 dB and 65535 for invalid
OK

Please let me know if this fit to your thought?
Thanks!!
Shawn