well it all depends on meaning.
i do not believe that MGMT wrote that agree to is not correct.
agree/conclude etc.. can use "that", but agree can be also agree with/to
hope it helps:
agree (up)on someone or something
to agree to the choice of someone or something. Let's try to agree upon a date.
agree (with something) (in something)
[for grammatical features] to match or go together with other grammatical features. The subject and the verb agree in number.
agree to something
to consent to something; to allow something to be done; to approve something. If you don't agree to my leaving early, I'll just do it anyway.
agree to disagree
Cliché [for two or more parties] to calmly agree not to come to an agreement in a dispute. We have accomplished nothing except that we agree to disagree.
See also: disagree
agree with someone
1. Lit. to hold the same opinion or judgment as someone else. I simply do not agree with you!
2. Fig. [for something] to be acceptable to someone as food. (Usually negative, referring to the disagreeable consequences of eating bad food.) Onions do not agree with me.
agree with something
1. Fig. [for something] to look good or go well with something else. This dress does not agree with these shoes, does it?
2. Fig. [for something] to be in accord with something else. Your analysis agrees with mine.