OK here is my dilemma.
I had an issue with a toilet at my job. I discovered that the toilet flange is not sitting flush on the tile. There is actually a space between the tile and the flange. Then, the flange is not secure with screws.
In all the years of building homes with my father and independently, our plumbers always had the flange right on top of the finished floor with no space under, and whether in a basement on a concrete slab or on a subfloor with wonder board, the flange was always secured with screw be in concrete or stainless steel screws.
My question is, is the way I have seen it done for years the wrong way?
Is the flange supposed to have a 1/4" space under it?
Is the flange not supposed to be secured with Tapcon screw to a concrete slab?

The assistance is greatly appreciated on this.

The flange needs to be sitting directly atop the finished floor and securely screwed to the subfloor or slab.

if it is a cast iron flange attached via lead and oakum, no screws are necessary.
nevertheless, it should sit ontop of the finish floor.