Thank you, Amit.
Currently, if WAL reconstruct page in another order it won't be a problem.
How can I check that it works? Would it be sufficient if I kill 9 backend and postmaster after commit and it will start normally executing select queries after restart?
I'll make a patch with missing spaces later. I also found some more missing spaces in PageIndexTupleOverwrite call and typo in comments ("on-place").
Best regards, Andrey Borodin, Octonica & Ural Federal University.