Poor WiFi Performance on iPhone

When migrating to a new router I remarked my iPhone (7Plus) had lousy TX performance compared to the other 80211.ac Apple devices connected to the same wireless SSID as revealed in below screenshot:

Since it was a new router, I figured maybe there was some inconsistent configuration going on somewhere. Reviewed everything; all good.

Comparative analysis: what's different about this iPhone than the other devices that are working correctly?!?!?

I remarked my iPhone was right next to the router. So I moved it about 4 feet away (in same room). Still terrible TX performance on just this one device. Other than proximity (which I just checked) which can affect wireless performance, why was this iPhone non-performant?!?!?

Nothing to do with the router in the end. The source of the fault was a Layer 1 issue with the iPhone itself (D'Oh!): the case was absolutely CRUSHING TX performance as the screenshot after case was removed from the iPhone shows:

Performance skyrocketed immediately after removing the phone's case.

I always figured there would some degree of a hit from using a phone case on signal performance, but I was absolutely stunned at actually how much there was.

Anyhoo, hope this helps others improve crap performance due to these snazzy phone cases we all love so much ;-)-

The offending case (wood with some sort of rubberized material lining it) is pictured below at Dan's request: