Yeah, it became a lot better proposition, when they turned out to be the Headcannon remakes. Like, those are ground up recreations of the original games with a lot of extra content. Assuming that this comes with all the previous stuff and S3&k has been given a similarly loving rebuild, it's a really good price.
Like, if these were just base-ass emulated ROMs, then, yeah, it'd be pretty shitty, but Headcannon has proven their quality over and over, so I have some optimism for this.
Yeah, calling them ports is honestly being a bit disingenuous to Headcannon. They are, as you say, complete recreations of the original games to be able to play and look exactly as the original game should, on HD hardware. The fact that they do look exactly like the old games, is entirely the point. Its actually fairly impressive all on its own, but they went above and beyond that to add, or in some case re-add, content is why these versions are so highly recieved. And tbh, these games are pretty much the reason Sonic Mania exists.