I dislike bikes with a lot of flop. I suspect a bike with 70.5hta and 50mm of rake is going to be annoying while standing on a climb. My understanding of why MTB's designers have been moving to slacker angles is because when the suspension fork is compressed, the HTA can get pretty steep. That doesn't happen on a gravel bike.
Negative trail sux. Hasn't happened to me much, but it will wake me up! Yes, on a gravel bike.
A big part of the slack MTB head tube angles is to give you long trail like on a motorcycle - its great for downhill at speed where you really need stability. Not so much for climbing.