I am not aware of any previous discussion of this quirky feature of Jet Set Willy 2 - it isn't mentioned in Andrew Broad's fairly comprehensive list of quirky features.
If you open up the attached 'JSW2 New Quirky Feature' test file, and try to collect the new Bathroom tap, you'll find that Willy gets stuck, with no hope of escape!
But in the other attached file, 'JSW2 New Quirky Feature not in original JSW', which has the exact same layout changes implemented to The Bathroom, Willy can collect the new item behind the newly-inserted walls, and get back out again.
Curious! The subtly different behaviour could form the basis of a frustrating trap in a modified game based on the JSW2 game engine! (Not with an item at the bottom of the hole, though, as that would render the game uncompletable without loss of a life.)
N.B. It might be prudent to have an occasional arrow come along at head-height, to put Willy out of his misery if he gets stuck!
Edited by IRF, 07 January 2018 - 12:08 AM.