I think it's pretty rare to see sloped keyboards these days.
You are quite right, and this is true in two ways.
Most keyboards today are "sculptured"; that is, as you say, they have "differently sloped keys by row", rather than "stepped", where all the keys have the same slope, differing from the general orientation of the keyboard, so that the rows of keys look like a staircase, as used to be the normal situation with typewriters.
But this is also true in another sense. A stepped keyboard can be achieved by putting the key on a bent stem, so that the direction of key motion remains perpendicular to the general orientation of the keyboard. Or it could be achieved by rotating the whole keyswitch, so that the keys are pressed down in a direction perpendicular to their surface.
This latter situation is also very rare these days.
It used to be true, at least for some IBM keyboards, that a keyboard could have sculptured keycaps on keyswitches with this stepped orientation. Signature Plastics used to offer such keycaps as one of their standard types; however, a visit to their website now seems to indicate they're concentrating on windows and insulation.