Template:S1 Pro Auto EQ
If you take a loudspeaker and put it on a speaker stand, then a table top, and then on the floor, the sound will change*. When the speaker is on a table top or the floor, it is interacting with the boundaries (table top, floor, walls and ceiling too). This means, if you want great sound in all situations you have to EQ the loudspeaker.
Bose tuned the S1 Pro to sound great in all four positions (speaker stand, table top, floor (both tilt-back and horizontal)) taking into account the boundaries. And the engineers carefully considered how you would be using the S1 Pro . That's why there are two settings for the floor (tilt-back and monitor).
I encourage you not to second-guess the automatic EQ. To use them in ways other than Bose intended you'd have to put the loudspeaker in a free field (a room without reflections).
But if you could put the S1 Pro in a free field here's what might hear.
⇒ Using the speaker stand position as a reference (basically, flat):
⇒ Table top: a little less bass than speaker stand
⇒ Tilt-back: a little less bass than Table top.
⇒ Horizontal: about the same as Tilt-back except there's some EQ treatment to support use as a monitor.