Keep a shower curtain and pressure rod handy.

If it ain't broke, don't fix it please.

Most people complain that gaps are too big but that does seem worryingly small

Can you show the full door design?

I have one that has loosened, but that is the first time I have ever had that happen, but not surprised since the glass/mirror guys for my build were really incompetent. Most of mine ended up with too large gaps and I had to find "gaskets" to contain the water on the bottom and sides.

If your guys did a good job, then I wouldn't worry and would enjoy the small gap. You will easily notice if it ever starts to sag.

Here is a full door and a hinge shot. Thanks for any insights

It looks good! You will notice immediately if it sags, so I would enjoy and not worry about it.