It’s a bit odd-looking, but why do you think it will leak? If it’s wobbly, you could mount a wood block on the wall that would span the gap between it and the back of the faucet and screw the faucet to it.

I wouldn't call it a professional job of installation, but unless you attach a hose to the faucet a give it a good pull, or pull hard on the laundry hoses, I wouldn't worry about a leak.

Call the local division of inspection and see what they say please.

It's bad workmanship - pure and simple.

Faucets aren't supported by the plumbing - they must be attached to something so that the pipes aren't stressed from the everyday use of the fixture.

The answer is to attach a block of water resistant material to the back wall and then anchor the faucet to it with the mounting screw hole.