I flew for various airlines in the days of RTOW tables. One always used wet performance in the belief it gave more buffer in the stop case. Another insisted you did both calculations and took the worse answer. So on a dry runway you also did a wet calc' and on a wet runway you did a dry one. If the dry was lower than the wet, on a wet runway, you used that.
Now with i-pads I've no idea what they do, other than plug the numbers in and accept what it spits out.
Different screen heights does seem to be a fudge for commercial reasons. Apparently it has not been addressed in decades. It would be an interesting answer to hear if anyone cares to ask the EASA & FAA guru's.
Fudge for commercial reasons: now where have we heard that before?
Old practices buried in the sands of time: now where do we see that every 6 months?