What muddies the waters here is languages like Java, where "10k lines" means "you've got a 10kLOC class there", and ecosystems like PHP's where while there's no

What muddies the waters here is languages like Java, where "10k lines" means "you've got a 10kLOC class there", and ecosystems like PHP's where while there's nothing in the language to require it, people and teams will insist on one class per file because hard rules are easier to understand and enforce than "let's let this area evolve as we increase our understanding". As long as what's there is comprehensible, being able to evolve it over time is a very useful lever.