Is this a shady Landlord

[Brettster]

Something dosent seem right here but I could be paranoid.

I'm moving into a 4 bedroom house where one of the roomates is leaving at the end of the lease, I'am taking their place. The lease is up for everyone July 31st and I'm moving in Aug 1st and everyone is re-singing the lease amendum for another year. The landlord wants me to give the dude thats leaving his 1,000$ security deposit and he said he will write up a statement that I'am now owed the 1k from himself(landlord) at the end of the 1 year lease. When i asked him why dont you just give him the 1k, he said that its easier to just do an extension and you buy-out his lease. Which dosent make sense to me because the lease is up, why not just make a new clean lease.