This is not a discussion about what's possible, it's a discussion about what's best. You can write your own opinion here, and it seems like we're in violent agreement, but that doesn't make our opinion GitHub's opinion.
That page is just one small part of a much larger reference document, and it doesn't seem opinionated at all to me. Plus there are dozens of other examples elsewhere in the same reference that are not simple invocations of one shell script and nowhere are you admonished not to do things that way.
And they show those patterns first. You had to take an example that is clearly about script permissions and misrepresent it. Yeah, it's not opinionated, it's fact. That's how it works...
At best, we are talking past each other. At worst, you are misreading everything I write to play gotcha games. Whatever, I'm glad you were able to figure out exactly the right things to do from a first read of a large and complex document that doesn't say anything of the sort. As for the rest of us mere mortals, we're stuck figuring these things out by trial and error, or even worse, having to pick up the pieces from somebody else's left-behind mistakes.
It's the reference manual. It's just a list of things you can do. If you like this specific thing, and think this should be the main way you express your build process, great. I think that too. Meanwhile with GitHub Actions you can also do this big pile of shit that the manual also describes: https://docs.github.com/en/actions/writing-workflows/choosin...
That page is just one small part of a much larger reference document, and it doesn't seem opinionated at all to me. Plus there are dozens of other examples elsewhere in the same reference that are not simple invocations of one shell script and nowhere are you admonished not to do things that way.