Many digital cameras are also able to snap a picture, and do so while recording video.
Many dashcams for instance when you press the event button they will also snap a single picture
If you are connected to a camera with the APP, it is not uncommon that it then override all buttons on the camera
Also as most video cameras do not use the full sensor size / resolution, a picture is often snapped in that sensor native resolution, many / most image sensors are actually in the 4:3 aspect ratio and not the wide 16:9 we most often see.
As a result the 16:9 video you get is just grapped from the senter of the sensor leaving unused pixels.
That if you have A LOT of unused pixels is also what allow cameras to do EIS ( Electronic Image Stabilization )
To get a ( 16:9 aspect ratio ) video footage, you need at least.
2.1 megapixel to get 1080 p footage - 5 megapixel to get 1440p footage and 8 megapixel to be able to get 4K footage, so when you record 4K footage on your phones 50 megapixel sensor it have a lot of surplus pixels, this can be used for EIS and or pixel binning where you bundle 4 pixels up to act like one much more light sensitive pixel, for instance night topography.
My phone only take 12 megapixel night shots as it bin the pixels 4 to 1 on the 64 megapixel large sensor, to be able to be more light sensitive with 4 X larger pixel artificially generated.
It would amaze me if the pard cameras are not able to snap a picture while recording video, but it could be they use even lower grade hardware that do not allow, which then just confuse me even more on their rather high price VS action cameras and dashcams or for that matter phones.
You can always grab a frame grab from the video, i think all / most players support that, that should also allow you to go frame by frame until you have that just right frame to grab as a Jpeg.