That is the point. Padding can't be inconsistent if there are only 7 values to choose from, not 1..7, but powers of two, so 0.125, 0.25, 0.5, 1, 2, 4, 8rem.
But having 7 rem-relative steps, that fit together makes the common use-case way easier: Joe: "I need more padding on this, so I use pa2 instead of pa1".
If you feel the urge to check your code base it's easy to write scripts that count the occurences of "pa1..pa7". It's not so easy if you have to take into account "padding: 1px", "padding: 20%", "padding: 3em" etc.