We can test this. So I did. I happen to have a pregnant character with low reflexes (4) and thus I can compute how long it should take to get to her max reflexes (20) using the the slow stat growth formula
on the wiki, which I have previously verified. For the character in question it should be 39 seperate +1 slow reflex gain events (which running at the Ten Ton Gym is).
So I opened an older save, turned on cheats, teleported her to New Texas, and gave her an Augment Weave Armor to make the process faster, and well, with both a gravid and bulky belly from the pregnancy the character did not progress past 50% of max reflexes (so 10, before modifications from the debuff), and losing the debuff did not recover the points gained from training reflexes before then. The modified save is attached if anyone else wants to test.
Note, the various screens round the displayed number the main stat screen rounds to the nearest integer, and the stat screen in the codex rounds to the nearest tenths place, this does not mean you gain stats faster.