No, this is a feature primarily of beef, some wild game, and poultry. Meats like pork and many kinds of fish may contain parasites and thus need to be cooked to higher temperatures than eg beef or duck (pork) or frozen before cooking (many kinds of fish) to minimise the risk of illness.
If we're talking about examined meats that come from certified source then I would say yes.
With a caveat - everything that have interaction with air should be treated as "surface". So if you buy gutted fish the "inside" should be treated as surface. Same with turkey (or chicken) for stuffing.
Marinades are surface treatments. However, many marinades contain salt. Salt does penetrate proteins. Over time, you will get a more "cured" flavor and texture. So, your pork might begin to resemble the structure of a cured or brined pork product. You may or may not want this result. On the other hand, some marinades contain ingredients that ...
The character is not good at cooking. He made all kind of obvious mistakes, like not pating the meat before searing it, burning the garlic, not drying the lettuce. So, anything weird will be attribute to his inexperience.
Sometimes you forget an ingredient when cooking something. If the ingredient is a spice, herb or flavor extract, you might sprinkle a bit of it on after the dish is fully cooked.
The character could also say, "Oops, I forgot to add the ___. I'll just sprinkle it on now, and you won't even notice the difference."
It's especially plausible if they ...
There are a few things that I can think that you might legitimately add after you've cooked the skewers:
fresh herbs, chopped fine (for color / decoration (aka. 'garnish') & to add a "fresh" quality)
spices that would burn over high heat (black pepper being one of them)
sauces, to add moisture. (especially those with sugars that might burn ...
It's very common to season steaks or other meats with salt and pepper after cooking, there would be nothing unusual about that. There are also seasoned salt mixes which people may use as well, that's also common. Using other spices is less common, there are finishing spice mixes which could be sprinkled on, which is less common.
As a writer myself I would ...