My 2018 Intel MBP 13" has the most amazing keyboard ever. 7 years later it still hasn't lost its crisp feedback.
I tested the M4 keyboard (14") in an Apple Store recently and, while it didn't display the looseness and rattle your video depicts, the keys certainly felt like they had a lot more travel and sideways movement than my current keyboard. At the time, I put it down to thousands of people passing through the store and banging on the keyboard to test it. The apple associate said, yes that's probably why, but I dont trust them any longer...at least in my market apple staff quality has plummeted like you would not believe.
If it's a regular feature when brand new, it's cause for concern...I have a M4 MBP arriving in a couple of days. It would be a shame if I had to return it due to something like this...as the specs on this machine are so awesome.