Not necessarily. There could be a little piece of crud stuck in the little port on the hot side of the cartridge or ball. I would shut off the water, remove the cartridge or ball,etc., inspect it, give it a shake in a bowl of water, etc. You would be surprised what you can find.
But first, another easy place to check is where the hot supply connects to the sink hose underneath. Sometimes there's a little screen at that connection, and it can get lodged with a piece of rust or crud. Disconnect and take a look.
One more thing you can try....get a helper for this.
Leave the cold side on. Turn off and disconnect hot side. Aim the "hot hose" from the sink into a bucket. Helper blocks faucet above with wet rag and turns on "cold" for a split second. This will route the water backward and down the "hot" side to the bucket. You might dislodge the crud and catch it in the bucket. Get it?
One other thing. Hopefully you checked that there are no kinks in your hot supply line. Did that already, right?
I replaced the 3/8" x 3/8" supply line already.
Wouldn't cold and hot come out slow if it were the faucet above? It's only the hot coming out slow.