If you can obtain part numbers from other sources, they often have parts but it doesn't come up by application.
I'm not saying this will always be the case, but on more than one occasion in the past year I've been able to find parts that are known to fit but don't show in the listings by application (use the part numer search)
I don't know if their software is perhaps able to curate listings to show you parts where they're bordering on overstock, or greatest profit margin, or a preferred warehouse (remember RA doesn't really own their supply houses), or if it's sheer incompetence or ghosts in the machine. IOW, a bug or a feature -- I DON'T KNOW.
There are of course the times when their system does not list applications for a part. I just ordered an AC Delco Advantage (aka Garbage) brake rotor. By application they listed several other AC Delco part numbers. We all know the AC Delco part numbers are the same and the suffix dictates the tier. So a 1234A is the "Advantage" bottom-tier rotor. They showed several other 1234 AC Delco rotors, but if you dig up the 1234A by part number search it reflects "no applications found."
If they were smart they'd generate a weekly report of "no applications found" parts and either input applications or delete the parts. Some parts are universal fit but something like a brake rotor obviously cannot be universal.