What? Fields is like 4 years older than Milroe. Fields turns 26 in March and Milroe just turned 22 back in December.
Milroe would be a high risk, high reward type of pick to take him in the 3rd round with the intent of developing him behind Fields. Am I confident it works out? No, but at the cost of a 3rd what's the issue? If you hit, you get your QB of the future without even having to use a 1st on it. If you miss, you only used a 3rd on him.
I'm personally not wild about Milroe in general after how bad his senior year was, but there's really no risk in using a 3rd or 4th on him and seeing if you can develop him behind Fields. Worst case scenario is that you just whiff on a 3rd or 4th, but they've done that plenty of times on worse gambles.