Very few people ever received the Jolla Tablet though, even fewer probably still use it. I understand that sucks if you happen to be one of those exclusive few but I can understand if they don't spend much time on Jolla Tablet only issues.
I'm afraid that's the only way to go if you want to support both past and future Sailfish OS releases - there is either just libpython 3.4 in SFOS <3.0.2 and only libpython 3.7 in SFOS >= 3.0.2.