Only found these but with no definitive answer:
https://security.stackexchange.com/questions/171494/is-it-possible-to-disable-the-fingerprint-scanner-but-not-the-button-its-on
https://forums.lenovo.com/t5/Moto-G5-Moto-G5-Plus/I-don-t-like-fingerprint-sensors-is-it-possible-to-disable-it-by/td-p/3729524
Seems strange there isn't much discussion around this, given the uniqueness and sensitivity of biometrical data and the blatant disregard companies pay to its protection (industry standard is to view user data as an asset not a liability - and regulator bodies aren't doing much about that either).
[edit]: Added final sentence