This feels like a bug to me, I've experienced the same thing: The scale value should stay as set by the user, rather than "resetting":
If I bring in multiple parts and scale them all differently, upon reopening the tool I'd expect those scale values to be preserved.
2c
Bots:
Makerbot Replicator 2x / Sailfish on Mightyboard
Custom C-Bot / RepRap Firmware on RADDS
Custom Tevo Little Monster / RepRap Firmware on Duet