sorry, my error. Yes have seen many instances of open on FindMyPast and closed on Ancestry. Ancestry also don't tend to transcribe the street if the top row with it is redacted, they don't look back at the previous or next page. FindMyPast do that bit better, wish they had done the 1921 to the same standard.
FindMyPast have an agreement with TNA, stemming from their original transcription of the 1939 register, whereby they can make alterations to the register entries, such as opening redacted entries, and send the updated record to TNA. So the data exchange between TNA and FindMyPast in relation to the register is a two-way street, and is completed regularly. Ancestry have no such agreement, and simply obtain updates from TNA on fixed timescales. I can't remember what that timescale is, whether it is annually, quarterly, or whatever, although I did find a reference to it at one time. But entries viewed on Ancestry are, more often than not, going to be behind any amendments made through FindMyPast or TNA directly and may not reflect the changes for some time.
When I have submitted opening requests to FindMyPast, as I said in my previous post, they are normally quite quick in responding and I have had a couple opened within a matter of hours. I have been able to view the entries in that timescale also, although I think they say that it can take 24-48 hours for the changes to fully propogate through their systems.