Not true.
The MCAT is the great equalizer used to compare students from a wide variety of colleges, but a good MCAT score cannot substitute for having actual pre-req coursework and having done well in the pre-reqs.
Applicants with poor GPAs but high MCAT scores do not fare well in med school admissions.
https://www.aamc.org/data/facts/applicantmatriculant/157998/factstablea24.html