So yes -- it was a snub in the sense that it was literally the least useful form of "help" they could've given. Julian didn't need symbolic help. He needed actual help, and the Guardian left him out to dry (and then proceeded to publish countless articles smearing him -- including flat-out lying as in the "he met with Manafort" case).
Heck, WikiLeaks sent one of their lawyers to help Snowden in Hong Kong when he got in trouble (and bought him plane tickets and the rest of it -- even trying to rent a private jet to get him out of Russia while he was stuck in the airport) -- and they didn't even have anything to do with publishing the Snowden revelations.