Why doesn't an acid-base reaction occur in basic amide hydrolysis instead of nucleophilic acyl substitution?

In the reaction of Grignard reagent with a primary and secondary amide, nucleophilic acyl substiution doesn't happen. The reason given is that R- is a strong base as well as strong nucleophile, an acidic H is present in amide and finally, acid-base reactions are much faster than nucleophilic reactions. However, in basic amide hydrolysis, nucleophilic acyl substitution is able to occur despite OH- also being a strong base and nucleophile. Why doesn't the acid-base reaction occur here?


