I'm only suspicious if they don't simultaneously and eagerly show me their Github so that I can see what they've accomplished.
Sometimes this industry is a lot like the "finance" industry: People struggling for credibility talk about it constantly, everywhere. They flex and bloviate and look for surrogates for accomplishments wherever they can be found. Peacocking on github, writing yet another tutorial on what tokens are and how embeddings work, etc.
That obviously doesn't mean in all cases, and there are loads of stellar talents that have a strong online presence. But by itself it is close to meaningless, and my experience is that it is usually a negative indicator.
Actually it is incredibly difficult, because you no longer have access to your previous employers' code bases and even if you do, it is illegal for you to show it to anyone.
So the person never does anything outside of his employer's IP? That's unfortunate, but as a heuristic, I'd like to see stuff that the person has done if they claim to be in a field.
Perhaps other people don't care, and will be convinced by expertise without evidence, but I'm busy, and my life is hard enough already: show me your code or gtfo. :-)
Also, unless you are in CA many companies have extensive IP assignment clauses, which makes moonlighting on other projects potentially questionable.(especially if they are assholes)
My previous job made it hard to even submit bugs/fixes to open source projects we used internally. Often we just forked b/c bureaucracy (there's a reason it was my previous job)
Not saying your wrong, seeing someone's code is nice. As long as you are aware that you are leaving alot on the table by excluding those that do not have a presence. (Particularly older with kids)