"alleges that the Action 3 supports vertical shot"
The original Action supported vertical shots. It's a handheld camera. You just turn the camera on its side. The Action has orientation sensors and realises the camera is on its side and rotates the video or still accordingly so that it's landscape or portrait and always keeps the image upright.
That was one of the main reasons I bought mine because the Action actually rotates the video in the camera while the GoPros after Hero 6 (I think) just recorded directly and added a rotation flag, which breaks a lot of video editing software.
You can hang you Action upside down as a dashcam and get 100% out of the box usable video.
DJI has confirmed the launch date for its next action camera. Seemingly scheduled ahead of the arrival of the GoPro Hero 11 Black and Hero 11 Mini, the DJI Action 3 should offer superior waterproofing than both GoPro cameras, among other features.