Hi Jhaysin,
Yes, that tool is just a simulation but still blocked, it’s enough evidence that it blocks anything that carries a name of the bot, Googlebot is just one of them.
And they confirmed, their server is configured to blocked malicious bots that use Google useragents. The question is, why the actual tool of Google (Google Mobile Friendly) is blocked as well? I only use the above tool as a comparison which then has the same result as the real tool from Google.

It will usually say, 403 not found, 500 internal error, or any valid error. But it says other error
, or unknown error
similar to that simulation.
This makes me assume their security isn’t working well as it can’t really see what’s a malicious bot.
Plus, it looks like they forgot to check the details of the logs. This has no Googlebot useragents
65.121.54.150 - - [25/Apr/2019:11:14:34 -0500] "GET /wp-content/uploads/2015/10/111209.jpg HTTP/1.0" 200 14233 "https://www.google.com/" "Mozilla/5.0 (X11; CrOS x86_64 11647.104.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.88 Safari/537.36"
They assume it’s a Googlebot since it has google.com, but if they will check the IP here http://whois.domaintools.com/65.121.54.150. It’s not accessed from google bot, Googlebot is still blocked. I think they should thoroughly test it 
Thanks!