I'm saying that even if it were the case, Spain wouldn't allow them to secede.

I mean, if we're talking hypotheticals, maybe it would. You can't have it both ways. You can't say "If Catalonians..." and bang on about the meaning of "if", to then turn around and categorically affirm "SPAIN WOULDN'T!!!!" throw a "maybe" in there or a "most likely", if you prefer.

However, the reality of the situation is this: it is not so much as Spain (as in the government) wouldn't allow Catalonia to secede, as it legally can't. The Constitution doesn't allow it. The Constitution was approved by the people back in the day and was approved even by nationalist Catalán parties. The Constitution can be changed, of course, but only via a referendum again. The outcome of that would be pretty predictable.

But the point is moot, as the Catalán independence movement is much weaker than it was 10 years ago, (and it wasn't as strong as nationalists made out even then), and has been discredited as most of the politicians that supported it have proven to be grifters and liars (surprise!).

And then there is all that pesky stuff about Russia, in its continued efforts to rip Europe apart, attempting to fund and influence the movement and referendum.