You (OP) stated that you played piano, but said nothing about playing guitar. 5 string basses can cause GUITAR PLAYERS fits because it disturbs the orientation that they develop on guitar. Cowboy chords, then bar chords all rely on orientation of the E and A strings. Though string numbering on a guitar is 1E 2B 3G 4D 5A 6 low E. In spite of that guitar players actually SUBCONSCIOUSLY THINK of the low E as string one. Playing 4 string bass is easy for most guitar players. Add in that low B string and the brain goes katywampus. The left hand is still seeking to orient on the lowest string and it is a cerebral experience to get the left hand to know where it is supposed to go.
OTOH, those not indoctrinated into guitar playing have no finger orientation yet. Learning the fingerboard from scratch will make it so there is little if no difference because you're at ground level learning. I was that guitar player who had an easy time on 4 string and was forced to take on 5 string... and it took some time. But now, I have five 5er's and one lonely 4 string that sits at my daughter's house in case I have to run a bass track for her.
But even if your fingers are fuddled with a 5 string now, STICK WITH IT. You will adapt over time. As you are just learning you aren't going to have to go out and perform with it in the next 20 minutes. So don't freak out because it's got 5 strings. And don't worry about the side of your hands. You will have to figure out the best height of the bass and angle of the neck (always use a strap for consistency sitting or standing). IMO a little higher position is better than a little lower to keep your left wrist straight and allow your fingers to extend.
Short scale? IMO don't bother unless you are really struggling. My first 5 string had a 35" scale length and a wide neck. I was certain I was going to return it within the 45 day return period. In a month I grew into it and didn't return it. For some things I play the longer wider neck better than necks with things spaced closer together.
And btw... below is a video of a little girl playing a full size 5 string bass. You will see that short fingers have nothing to do with playing accuity.