Thanks in advance!
I've just had a look - the site asked for a Bitcoin address (I entered a fresh one), then presented me with three captchas. It looks like it's just a standard faucet, so I'm assuming it'll pay the 15k satoshi direct to the address I entered. I couldn't see anything obviously scammy about it, unless it's getting me to complete captchas which it then uses elsewhere. I don't think there will be a withdraw function, because they ask for a Bitcoin address. I'll edit this if I don't receive the 15k satoshi...
Edit: well, over 24 hours have passed and there's no sign of any payment from littlebits.xyz. I'm inclined to say the site is either non-functional or it deliberately harvests captcha entries. Either way, I'll be avoiding it in future. If anything changes I'll update here.