The belt install procedures says the belt tension is supposed by be checked and adjusted to spec again after running the engine for 5 minutes. Maybe they forgot to do that. Ask them to re-adjust the belt tension. Another common mistake is to not get the belt ridges lined up with the pulley ridges correctly, often offset by one ridge to the side.
The belt replacement is spec’d at about 1/2 hour so it is hard to understand why a dealership would find that a difficult job. I expect they used one of their trainee staff for the job, and this was the first time they had done it. It requires a special tool, SST 09249-63010. Maybe the shop tech did realize this or they don’t have that tool for some reason.
Here’s a question for the folks here. The instructions say “slow turn the belt tensioner for more than 3 seconds” . I could see turning it more than 30 degrees, but 3 seconds? What’s that about?