VelH is the .csv column that shows horizontal speed. The documentation is a bit arcane. I'll change that.
I was able to retrieve the .txt file from my iPad DJI Go App 4.0. Didn't have any problem converting it to a .csv. The .dat on the tablet isn't the same as the .DAT on the AC and can not be processed using CsvView/DatCon.
Ok so I see what my issue was. The mph displayed on screen of the dji GO4 App displays mph as fps (feet per second). So my 64.5mph was actually, 40mph. The GO4 App has had several updates with plenty of opportunity to correct a misleading issue. I bet if the display stated the a/c was traveling slower then it actually was, they would've corrected it a long time ago. No they would rather allow everyone that doesn't know better to post in social media about how fast they're able to fly.
It's no wonder why the Flight Autonomy does not function properly at times.