Adding to the other answers, I played in a group for a few years that liked to take music "a bit" faster than normal, for stylistic purposes, and we would often count 4/4 music in 2 (or 3/4 music in 1) because it was just easier for our leader to count off the tempo (from the piano, often by nodding) when counting at a slower pace and not give herself whiplash. But even if we were counting 4/4 in two, we still played it as if in 4/4 (giving it 4 beats per measure instead of two).
Of cousre, this was the same band leader that would ask us to play in the style of "bad 80's rock music", so perhaps she wasn't always giving us instructions in the most formal music theory lingo possible (although she did know her theory as well).
The problem I have with "played twice as fast as written" is that it ignores the stylistic difference of 4/4 played twice as fast as 2/2. For beginners, this may not matter as much, but it is still there, and we shouldn't confuse them.