I've taken the liberty to add a "Closes" for the other PR that I mentioned in my original comment the PR description.

IIRC the reason the stub hash exists is to not require PHP-Parser (which requires network to download) for non-dev builds of PHP. I think this change is going to break builds in environments that disable network access (i.e. typical distro build environments).

Using the stub hash is also very practical to avoid regenerating everything (which indeed takes a bit of time), when not directly addressing a single file. In the very most cases, not force regenerating is exactly what you want.

IIRC the reason the stub hash exists is to not require PHP-Parser (which requires network to download) for non-dev builds of PHP. I think this change is going to break builds in environments that disable network access (i.e. typical distro build environments).

I fully agree with @nikic, downloading the PHP-Parser bundle when not necessary is counter-productive.

You can't rely on the files timestamps to be correctly aligned, even when unpacking a dist tar.gz file. So depending on which file, between arginfo and stub, takes the fresher timestamp, you would end up with different outcomes.

Related to this, I just updated my PR #20891 to align the file timestamps even when hash check determines there is no need to regenerate.

Thank you everyone for the feedback. I'm closing this.