depends what he means by "most". depending what source you look at, chrome has the majority market share so even if it's the only one to implement it, it still counts as "most".
"most browsers" would become "the majority of browsers". If there were 5 browsers, "the majority of 5 browsers" would be "3 browsers or more". It doesn't make any difference which ones are most used, the sentence (apparently now changed or removed) wasn't "most of the requests will be protected", or even "most users will be protected"
In Germany, nope: https://clicky.com/marketshare/de/web-browsers/
Germans sure love their Firefox. Now, that may not matter for you depending on what market you're targeting but not everyone is as lucky.