I have no context for this example, have a link? I’ve seen the crazy kitchen at the Museum of Science and Tech in Ottawa that has a similarly themed illusion, but in that one the floors are level but painted in a way that tricks your brain into thinking its angled, but its not, which is 100% illusion.
Thus what I am imagining for your example is that the floor is in fact angled, but the paint makes it look straight, so the short person is infact elevated above the tall person in a way you cannot tell, creating an effect where perspective due to a physical difference makes you think they are on the same level but the illusion provided by the floor messes with that, creating an illusion that is really just perspective.
But there is no trick in this post. You know you’re tilting the phone, there’s no illusion. Its pure angles and you’re completely aware of what is occuring, thus no illusion. The definition of illusion is pretty clear, what you are seeing must be false or erroneous.
noun
An erroneous perception of reality.
“Mirrors gave the illusion of spaciousness.”
An erroneous concept or belief.
“The notion that money can buy happiness is an illusion.”
The condition of being deceived by a false perception or belief.
“spent months flailing about in illusion.”
There is nothing erroneous about this perception.