Those are not picks for playing banjo with picks as we do, actually they are made for people that like to play with their fingernails and don't have any. That little arch goes where the fingernail normally would be and you pick with the underside of the pick, as you would with your nail.
If your intentions are to play bluegrass on your banjo I think they would be a waste of money. Why not use your bare fingers if that sound interests you or a traditional fingerpick? They are making quite a number of fingerpicks these days that aren't uncomfortable to wear.
Playing Banjo, fine. I guess you can get used to anything if you use them all the time. If you want to play Bluegrass, good luck. They look like they would bend if you play anything driving, fast or with any kind of force. my 2 cents...... I wouldn't use them on a bet.
Think of it this way, if they worked better than what everyone is using, then everyone would switch to them. If they worked as good as what every one is using, then at least we would know about it and some people would be using them. If they sucked, then people who've tried them wouldn't keep using them, and probably wouldn't tell anyone about them. I've seen them in the catalogues and websites quite often, but so far, have never seen or heard of anyone using them for banjo. So I'm betting they suck. From a personal experience viewpoint, I used to use Alaska picks with guitar. I tried them with banjo early on and they didn't work at all. I couldn't get any drive or power, and it was like a ripping my fingernails out kind of torture.
Finger Picks are cheap enough to buy them just to see if you like them, I have a little bag full of the ones that looked cool but didn't work for me but I'm sure the next cool ones I see I will buy them just to see if they work for me. Go for it, what's a few pounds between friends.