Again,
Few DMM have 1M input impedance
Is it problem?
Such a problem, could well be minor, compared to the (probable) lack of safety features on many very cheap multimeters. Which could lead to them exploding and injuring or killing the operator, if accidentally connected to a powerful enough, high voltage supply.
I've seen teardown video(s) of that DMM, and it seems to have these crazily tiny fuse(s). Which I suspect, may not have anything like the safety of proper full sized HRC fuses.
tl;dr
You are worrying about one specific fault of these multimeters. Apart from the (probable) lack of real safety capabilities, they probably have many issues and limitations, compared to proper, expensive quality branded multimeters.
But I haven't got any such DMM (AN8008), so could be wrong and or biased. (partial Fluke fan-boyism etc).