It's quite obvious that bonus stay/nights from spg are currently not added when combining account.
Question now is if the IT team is aware of this ? Any lurker can confirm?

I would definitely steer clear of combining accounts if you have 2x stays/nights that are not showing (my problem also). I've lodged a case number for my missing stay credits and until that's resolved I won't touch anything else.

A CS rep from the SPG side even told me yesterday that if you combine accounts that will preclude qualifying under the SPG legacy route! I take everything I hear from CSRs with a pinch of salt in this chaotic changeover but I've certainly seen and heard enough to make me hold fire on combining accounts.

Data point, combined my account today, the double nights were added. No issue with that. Thus managed to hit 50nights with this.

Those that intend to qualify via double stay may have an issue though as there is still no stay counters anywhere in the site or app.

Yes, my nights count changed today (nothing to do with a/c combining) and the total now includes all the double nights correctly. However, I do need the double stays to qualify this year - my winter vacation got pushed back to 2019 so I won't manage to rack up the nights in time. For stays, I'm only 4 short, which is mattress run territory if need be, but the shortfall goes into double figures without the double stays I had registered on the old SPG dashboard. So I'm kinda sunk for Plat qualification if I can't get these added back somehow.

Just outright dumb to remove all the stay counters when one of the official qualifying routes is number of stays!