phpBB uploaded file permissions vs. W3 Schools php upload file permissions

I'm moving my phpBB board from a shared server to a VPS running Ubuntu 20.04. I previously had issues with file ownership, that has been tackled through the help of this Forum; many thanks to those that helped me. I'm now trying to solve a file permissions problem.

On my legacy board running on the shared server, uploaded files have 644 permissions - as they do when I port them to the VPS environment. However, files uploaded in the new VPS environment have 666 permissions. But the code sample from W3 Schools for PHP uploads, running in the phpBB directory, will upload files into the same /files directory with 644 permissions, as I would expect. I would have expected the umask of 0022 in my Apache envvars to constrain the permissions with phpBB, as it apparently does for the W3 Schools code, but it doesn't. (I've also posted this inquiry over on phpbb.com, but I've yet to get a response.) Any ideas about where to look?