Yes, that's a community-maintained wiki article with a few editors
(at least most of whom are also DDs in this case), started in
2017-03-22 to describe a specific model which discourages it, but
nowhere does that claim use of /etc/apt/trusted.gpg.d is officially
deprecated and when, much less link to official documentation
stating so. The article also does essentially nothing to explain the
risks that model wants to counter. Reading between the lines, it may
protect you from accidentally using a package repository (whose
maintainers you implicitly trust) in unintended ways. If the people
in control of those keys wanted to take control of your machine,
they still could, so it's not protecting you from any intentionally
malicious threats.
It might be good to get input on this from anarcat and dkg, as the
primary authors of that document, on the underlying intention, and
maybe add some further explanation to it indicating the real-world
threats this recommendation mitigates. Security policy should be
informed by risk analysis, and complicating things with additional
security controls which bring no appreciable improvement to the
actual security of the system but just "because you can" is
ultimately detrimental.