After TWO months of interviews and back and forths online, then in person at the office, they ask to do a product exercise to recommend improvements.
After delivering the ask - and I consulted with peers to triple check I was on point - they took the work and went with an internal candidate.
Typical terrible practice, one wouldn't want to work there after their lack of professionalism through this process.
I dodged a bullet. Good riddance. Tell me where I can send you a bill for my work.