No, it's not orthogonal. I can see it in things like the complaints about how foreign keys "caused problems" in the migrations. Generally, that means one of two things: The foreign keys were actually
preventing bugs in your migrations (which even in a startup context is a Good Thing(TM), as "buggy migration" is effectively slower than "correct migration" no matter how fast the buggy migration is), or the developer was not experienced enough with foreign-keyed databases to really know how to migrate this.
Bear in mind that if you screw up hard enough there's no guarantee you can recover. Anybody hanging around this site for long enough has read at least a couple of stories about the technical error that brought the whole startup down because there weren't enough resources to recover, and "botched database upgrade" (combined with "failure to backup", which of course occurred because there was no time, we're going too fast and we're too awesome!!! to do the backup) is a prime candidate for that sort of event.
I say the latter because I've been there. Setting up foreign keys is one skill. Learning how to migrate them is another. I've screwed it up before. It does take a bit of learning. But once you learn it, you're still better off using them properly in the first place. There's also some skill in learning how to set up your database so it can be migrated; I'm not even sure how to begin putting it into words, but there's definitely some skill involved there. (I'm not guaranteeing I've got it all figured out, but I've certainly improved, which is enough to establish that it is a skill.)
They're not equivalent either, certainly, but when you say "orthogonal", you're making the claim that they are not just different (which is true), but utterly unrelated, and that claim is unsupportable. I've been deliberately spending my last couple of years learning how to build things both fast and right, and I've gotten to the point where I can spank anybody just "hacking around" after about a two-month window, after which it's all profit. In fact I'm building a system replacing just such an effort right now... well, after I stop posting this anyhow. My system isn't a glorious paragon either because as an experienced developer I know where to cut corners to get it out, but it's a lot stronger than the hack job it's replacing (and I'm doing it in less time, too).
(Part of the reason I started this learning is that I was at a startup where I did in fact make this exact error. In the end, this is not what killed it (what killed it was the management insisting that there was always just one more feature we needed before release, and then once we had that, there was just one more, repeat until out of money with no customers), but I've made this mistake and I won't make it again. But the alternative is not hackhackhackhackhack, the alternative is being more familiar with the cost/benefits ratios and picking the winners, some of which will still be "do it right", and some will not. Hardcoding the answer in either direction is wrong, as it pretty much always is.)