The manufacturer recommends dry cleaning but "every source" you've consulted says that it's ok to wash that linen suit.
Apparently, "every source" knows more about the fabric, construction, dyes, sizings, etc. of that suit than does the manufacturer of that suit.
I'd recommend following the manufacturer's care label. On the other hand, if you want to pioneer the "vagabond look", go ahead and wash it.
PS: Don't believe everything you read on the internet.