Top is 85, background is larger (less far away than it would appear with the wider 50). I'm just agreeing you can get very
similar shots, though the working distance is quite different.
With regards to the perception of depth at various focal ranges (and why wide angles aren't the best for portraits) below is a sample with linear subject matter.
My goal was to keep - as much as possible - the same framing of the subject. I used the top corner of the board, the top of the last rook, the square in front of the bottom pawn and the base of the closest rook as my framing guide to set the appropriate distance and height. EDIT - forgot to mention, focus was on the King.
90mm f8.0
58mm f8.0
and 31mm for good measure f8.0
Note the proximity of the subject to the lens needed to capture the same shot forced the subject to be longer to the wider lens, also causing the depth of field to
appear less.
Also note the top left corner, some empty cans. They appear larger in the 90mm shot. The relationship between the subject and background is dramatically different.