In a few industries, for industry-specific reasons, who appears on credits and the exact contents of those credits actually does matter for career advancement purposes. Video games are one of those industries. Film and academia are two others. It is critically important to your future if you're an assistant professor or software developer working on the 3-D engine that your work get recorded in the industry-standard manner. It is difficult to appreciate this if you're not in academia, but getting your name listed first (and not second!) in the paper edition of a magazine that no one reads is actually really important.
Many of the rest of us work in industries without this professional norm. That's wonderful for us, but does not itself fix the problems of this norm for people affected by it.
There is no industry-standard record of credits in the games, JFYI. Mobygames is a good collection of crowd-sourced info, but it is far from being comprehensive (even major AAA games and/or their credits can be missing). Without a proper record credits cannot be that critically important and they are not from my experience. Nobody is going to find the games you said you have been working on and play them through to get to the credits to verify. Your experience is supported by references (formal and otherwise) and your portfolio if you are an artist or a designer. Credits are just bragging rights.
Now, if there had been some kind of official record then credits might have had a bigger weight but, with a lot of people's experience being in unfinished/cancelled projects, still it would not reach the level of critical importance IMHO.
There is no industry-standard record of credits in the games
No, but that doesn't mean people don't use it as hiring critera. Some software companies use github profiles to screen candidates. Open source contributions in general, and github in particular are a comically inept way of evaluating candidates, even in comparison to credits. But it still happens.
It sure does not. People are free to use whatever criteria they want for hiring. Even illegal ones would be impossible to prove as long as they are not advertised. But neither this nor the fact that some companies outside the games use github as a criterion proves that credits are important. What you can do is important. What you have already done is too. Credits in movies and academia are an expression of these things. They are not in the games though.
Notably, Rodriguez is no longer a member of the Director's Guild Of America - with a number of knock-on effects including being unable to work for most of the major studios - as the direct result of a disagreement about credits.
Many of the rest of us work in industries without this professional norm. That's wonderful for us, but does not itself fix the problems of this norm for people affected by it.