Unless you're building the next OpenAI or Google, I wouldn't care HR and lawyers. But it is always wise to work on personal stuff on your free time, personal computers, etc.
yeah, but if whatever the guy was talking to is something other than a toy hobby, if it's the foundation of real business value, almost any moderately sized business would fight you about ownership.
They will have really hard to prove that.
all they need is more lawyers than sense. To grow a business, thats typically what you need also!