The short version is that any attacker against whom certificate revocation might matter is by definition in a position to MITM connections, and can simply interrupt the certificate check.
And the correct interpretation of ‘interrupted revocation check’ is ‘invalid certificate’. Now, of course there’s the problem that the CAs are apparently unable to provide constantly-running OCSP servers, making such an interruption more likely to be due to technical inadequacy of the CA than due to an ongoing MITM attack, but that is first and foremost a problem of the CAs, not of a browser vendor.
Congratulations, you just broke every user accessing the Internet through a captive portal with an HTTPS login interface, and every user trying to access the Internet through crappy proxies. Which is one of the reasons why other browsers don't hard-fail on revocation checks.
And what exactly is the alternative? If any intermediate proxy/captive portal can say ‘oh, everything is fine’, how are we going to protect against MITM attacks?
Out-of-band online CA checking is a weak design that doesn't work in practice. If revocation is required in a strict sense, then the solution will look something like "nuclear HSTS-style OCSP stapling". But to my mind, a simpler alternative would be for browsers to support something like TACK, so that instead of trying to knock down known-bad certificates, we just had a much better infrastructure for asserting which certificates are good.
All that aside though, it's awfully silly to kick Google for noticing and pointing out this security problem with revocation checking. Other browsers are often literally pretending to do revocation checks that aren't actually meaningful.
I wish Cloudflare or Google would get into the CA game; they'd be more than capable of doing OCSP checks on every use, and could issue very short lived certificates otherwise (weekly?)
OTOH that just leads to completely trivial DoS attacks (AFAICS, at least). Of course that's a lot better than trivial MITM, but it's still not exactly "good".
The short version is that any attacker against whom certificate revocation might matter is by definition in a position to MITM connections, and can simply interrupt the certificate check.