What do you mean? Just because it's in the standards doesn't mean they are treated as the same address, does it?

I don't see anywhere that myaddress@email.com and myaddress#this@email.com must send to the same mailbox. I only see that an address must "[contain] a locally interpreted string followed by the at-sign character."

Of course, this means that you can use - or ~ or # in your address but they don't have to be treated (and probably aren't) treated as the same address by most email systems.