[henrikeh]

Since you say “commercial” software I’m confused. Would that exclude medical software, aerospace software?

If what you are getting at is that it is not widely used/not used in anything “successful” and thus just a pipe dream, then I understand your concern. But that doesn’t mean it can’t be a useful strategy for some fields nor that it couldn’t produce more reliable systems.

[gomox]

I wouldn't exclude anything, but if the only examples of this are those kinds of highly immutable, mission critical software I think that would speak volumes about the practicality of maintaining a spec (the approach OP was pitching).