is this a new way to scam?

The newish thing is people listing shit games with "fake" market items designed to look like expensive items from TF2 and using those to scam people.

In my opinion it's best to report the user to valve and include the details.

As a 11 year Dota player, my guess is that he saw you have a Geomancer avatar, he asked you if you were good and then he gave you his account to boost him, or at least his Meepo stats. I've seen a lot of random people asking other people to boost them so they could either play Dota at much higher rank or simply to ruin high rank games for the good of "My team is cancer" agenda, so I don't believe he wanted to steal anything from you, except your time and effort. Either way, stay away from that account..

Personally if someone tries to add me and I see that their name is "I got a big dick".... well I already know what to expect.

You should use cheats on purpose to vac ban the account he gave you, so he can't scam other people with it.

Before deciding if it's a scam or not you should consider that, the sale or trade of Steam accounts is forbidden, any which are found can be locked down along with any other Steam account you may have.