Thanks, all, for your input. Here's more data, from my experience...
Tues: Used my BCV transferred points to at least hold 2 studios and one 2BR at BCV (3 rooms total) over what I figured would be a popular wkend (July 9-10) until my BWV points reached their 7 mos window and could be used to add extra nights to make each room a 6-nt stay. I could SEE the BCV points in the booking tool - but could not use them to complete transaction (per my memo above) so I called MS to complete it.
Wed: Called MS to fix a grossly misspelled name on a ressie (app would not let me modify any names; produced ERROR page).my Asked if having those BCV points on ressies would make EVERYTHING about those ressies more difficult (because if so - then future state, I may wanna put all 150 pts on the 2BR so that only 1 ressie is affected!) Naturally she said no it shouldn't... to which I said well in theory - the calculator on your booking tool also shouldn't have told me that I can book July 9th vacation on Dec 8th... but it does! (MS did not believe me... had to prove it on phone with a couple different dates.) Just as a lark I then tried to add a night to a BCV ressie using BWV points that were still one day too green - and I did NOT get the usual "you are outside your booking window, try again later" prompt, but instead got the weird "This Resort is No Longer Available" message that popped up with all the other transactions I attempted to do with the transferred points or their ressies. I said please put in a notice that website booking calc is not right, and I'll give your app a try on these modifications at 7am CT but if it fails... expect a call at 8am CT sharp!
Thurs: Got online 7am and whaddya know- THE APP ACTUALLY WORKED! Was able to add necessary nights to all 3 ressies. The name modification window was also magically released - however - it kept freezing on me, so that's likely a web thing, not a transferred pts thing. But modifications were not without oddity. When I added days on first reservation, it showed the BCV transferred pt contract first, with the BCV transferred points already assigned to that ressie (35) plus the additional 15 still not yet used in that contract's "inventory". It AUTOMATICALLY made me use those first (put a "lock" on that contract at top of contract list and literally says "these MUST be used first"). Then it listed my 2 BWV contracts for additional points to use under that, which I could prioritize per usual. Fortunately, I WANTED to use up all those transferred pts first, but if I hadn't there would have been no recourse except to call MS. The other 2 ressies also showed the BCV contract first, locked in place with whatever BCV points were already allocated to that ressie. After I secured all ressies - my BWV point balance appears correct all in 2022 UY. Howevr - if I go to booking page, it shows both BCV and BWV as my available "home resorts" and then says I have 0 points (which is true for BCV... but should show plenty still for BWV!) The BCV point transactions do not show up in the points transaction app page which makes the changes involving the BWV points VERY confusing as numbers do NOT add up - you would have to know there were other "mystical" transferred points involved to make sense of any of it.
Bottom line... I got my points, and a bit of a headache using them - but I got our ressies! I am VERY glad I did the transfer, especially as it enabled us to at least secure the busiest days before everyone's 7mos window opened on them. Turns out the nights we needed for a 2BR and 2 studios are already gone/booked up for the first night or two of our stay! And with the borrowing restriction still in place, a quick infusion of points (with no dues attached!) was a huge plus. So I'd do it again... but hopefully no time soon!
