Not sure what you think PPI means or how it’s calculated, but it has nothing to do with being a tv or a monitor. It’s a relationship between the number of pixels and physical size.
A 34" 1440p monitor will have a lower PPI than a 4k TV at the same size
Pixel density is pixel density. Doesn’t matter if it’s a tv or a monitor.
Sure monitors typically have less input lag and there are reasons one might choose a monitor over a tv, but the reverse is also true. I chose a 55" tv for my sim racing setup that sits maybe a meter from my face and there’s no problem with that setup
There’s another factor which hurts them but also makes them great. You only ever need to buy 1 pair. The build quality is phenomenal, I’ve had mine for 10 years and they look brand new.
If I had to buy another pair I would (well, not anymore I guess). But beyerdynamic headphones are in the ‘buy it for life’ category