Interaction of suspension and alteration

Hookpad is pretty strict with it’s chords. When you select #9 alteration the b9 one gets grayed out, even though in jazz theory you may do both. The same goes for #5 and b5. So the alteration implies changing a pitch. Then why would suspended chords allow you to have both the altered pitch and
the unaltered one. On the screenshot you can see that the Fsus#9 chord for some reason has G in it, a natural 9th. Which not only sounds quite discordant but also makes no sense. Sus#4 also shows the same behaviour, adding both natural and sharpened fourth.

And I feel that surely this should be already documented, but I couldn’t find anything on the forum.