When you are in the overworld and run the command:

/execute as @s at @s in minecraft:the_nether if entity @s[distance=...1]

It returns "Test passed", but you are not in the nether.

But if you run (replace USERNAME with your name):

/execute as @s at @s in minecraft:the_nether if entity @p[name=USERNAME,distance=...1]

the test fails.

/execute as @s at @s in minecraft:overworld if entity @p[name=USERNAME,distance=...1]

works on the other hand.

Maybe the bug also exists in earlier versions but I haven't checked this.