Would you please elaborate on both of sentences "They're too good people to do something like that.
This is as good coffee as that."
in terms of grammar?

Some grammar books say Plural or UC noun with attributive adjectives can’t be used in between too…to & as…as. Only a singular countable noun can be used, as shown in the structure “too+ adj. a(n) noun+ to” or “as+ adj. a(n) noun+ as”. If we want to put Plural or UC noun in between “too…to & as…as,” we have to add a quantifier immediately following too & the 1st as, like There are too many people here to be quiet. or He put as little effort into this project as Mary did.

In brief, the key question is whether the statement of “Plural or UC noun with attributive adjectives can’t be used in between too…to & as…as” is grammatically correct or not?
Thanks in advance.