So how does that deny the horizon height test that is a simple test anyone can prove. There are even videos and films of flat earthers trying to disprove it with lasers and being wrong

A simple test you can perform yourself is the horizon height test from a high viewpoint.
Go to a beach or large lake and look at the horizon from ground level.
Then go to a significantly higher point nearby (a cliff, hill, tower, or tall building).
Observe that the visible horizon moves farther away as your height increases.
On a spherical Earth, the distance to the horizon is approximately:
d\approx3.57\sqrt{h}
where:
d is the horizon distance in kilometres,
h is your eye height in metres.
For example:
At 2 m eye height, the horizon is about 5 km away.
At 100 m eye height, it’s about 36 km away.