Wierd. Phone interview after a Final Round?

I forgot to ask if anyone has heard of something like this. They also gave a pretty strict timeline of being in contact within 72 hours.

I've heard of this happening before. In my experience it happens to candidates who made a good impression with the people they interviewed with during the final round. I'd guess that there aren't enough positions open for the job that you interviewed for, but an interviewer recommended you to someone else for a different position within the company. Either way, you're still on the fence with them. Get back in touch and be prepared as you would with any final round interview.

I had something similar ... Remember: HR loves having a high batting average (acceptances/offers extended) so don't be afraid to outright tell them that they are your #1 choice because if they want to gauge your probability of accepting. The key idea is to do this without sounding desperate or pushy, so just mention how they have continued to stand out and impress you vs other banks throughout the entire recruiting process.

You have a very good chance of getting a job, but it may not be in the division you initially applied for. Either way, its a very good sign. Good luck.