One of the areas at my work is labeled E621 as part of the identification scheme they use where I work
The giggles from this that know is always a treat especially considering the person manning that station has no idea why some people giggle about it and in general is a stick in the mud.
Definitely have not had the same experience. I'm not sure where you are looking that this is getting through your blocklist. My only guess is that things are not being tagged properly on initial submission, in which case you should limit your search to only include posts after they're a few days old, so that people have time to catch and fix this.
Ima be real the reason you're not seeing it is because you're probably so used to it that it doesn't even register for you. Either way, don't really have a skin in the game, I quit a long time ago. Maybe it's gotten better maybe it hasn't. I don't really care, i've already been turned off the site.