Extra Recommendation Letter

I’m applying to University of Michigan and I see explicitly that they require 1 recommendation letter. At my school, we are all encouraged to have 2 letters, one from a STEM teacher and one from a humanities teacher. The website says not to submit any additional information or else a decision will be delayed, but my counselor has advised me to submit both. I was wondering how long my decision will be delayed if I submit two, and should I even submit two in the first place?

Thank you!

Your counselor has given you advice.

Personally, I would take that over the advice of strangers, many of whom are high school kids.