No, the saying does not hold. Microsoft didn't buy "many eyes"; they bought a relatively small number of very specialized eyes. At any one time in the mid 2000's, something like 4-5 security firms did $1MM or more in a year at Microsoft, and those firms each had between 15-40 people working at them --- and no firm did 100% of its business at MSFT.

What happened at Microsoft may not disprove this folk wisdom about defect detection, but it's evidence against it, not for it.