Too many things occurred within short time periods, its hard to be certain. For instance the initial fire department spraying of pools started on the 19th but they started with reactor 3 pool, and if I remember correctly they didn't start on reactor 4 pool till the 20th. Somewhere around then they also pumped water into reactor 2 fuel pool using an existing piping system. It is also quite questionable as to how successful these spraying attempts were, we saw video of some parts of reactor 3 spraying at this point, and it was a bit of a struggle. Only with the arrival of the concrete pumping equipment did confidence increase that the pools were being replenished effectively.
The same is true for one of the other factors which caused unit 4 fuel pool concerns in the first place, the fact that the estimates for release to the environment were so high on that day, and detected levels on site rose considerably. But since something happened at reactor 2 on the same morning, its not possible to attribute this to reactor 4 pool with any certainty.
I don't like to draw solid conclusions due to the quality of the data and unanswered questions, the fuel in pool 4 may not be in completely perfect health. But if some of the really bad scenarios for this pool had readily happened, I would have expected to see more evidence of this by now, rather than workers busy operating in that area of reactor 4. The possibility of the pool collapsing seems to have been a real enough risk that they spent time constructing a support structure underneath, but once this was done my attention largely turned elsewhere. If some new piece of data or fact emerged I would take interest, but most of the big questions I dwell on these days relate to reactor 2. And at some point more detail of reactor 3's fuel pool will become clear, which may or may not be noteworthy.