Yes. From experience, for a relatively complex system, 1k+ line PRs from mid-level devs without tests are almost guaranteed to have bugs; often nasty ones which can take many hours to identify and fix.

I remember when I started coding (decades ago), it would take me days to debug certain issues. Part of the problem was that it was difficult to find information online at the time, but another part of the problem was that my code was over-engineered. I could churn out thousands of lines of code quickly but I was only trying to produce code which appeared to work, not code which actually worked in all situations. I would be shocked when some of my code turned out to break once in a while but now I understand that this is a natural consequence of over-complicating the solution and churning out those lines as fast as I could without thinking enough.

Good code is succinct; it looks like it was discovered in its minimal form. Bad code looks like it was invented and the author tried to make it extra fancy. After 20 years coding, I can tell bad code within seconds.

Good code is just easy to read; first of all, you already know what each function is going to do before you even started reading it, just by its name. Then when you read it, there's nothing unexpected, it's not doing anything unnecessary.