Yes LL is based on Ubuntu but LL wouldn't prompt to upgrade Ubuntu, let alone across architectures (32/64).
I too have a LL 3.8 32bit, ran updates to confirm - nothing for ubuntu
Could be something was installed that added the Ubuntu repo's or the repo's were modified for a PPA or
?...
Any how, I wouldn't suggest updating...
Other may chime in... but that's my plugged nickle
Good Luck