That's a special case in how Bio's epic feats work. You're using one of your "every third level" feats for it, but it lets you choose from the special rpic feat pool of the class you're levelling in even if that class isn't actually epic. You can do the same thing if you have the requisite feats and take a level of fighter at the appropriate time you can get epic weapon spec with as low as 5 fighter levels. I think it should be considered a bug but whether Bioware does or not is another story.
If you tilt your head far enough and squint hard enough, anything becomes as simple or complex as you'd like--regardless of whether it is or not. -- A lesson learned from Stephen Wolfram's A New Kind of Science
strange that this doesn't work for epic spellcasting. i have a build right now that is a level 20 cleric level 3 bard level 2 PM and i know i have to wait until level 11 PM before i can learn an epic spell even though a) i'm an epic character and b) i am currently leveling up as a PM which is a class with access to epic spell. or at least that is what it seemed like when i tried out this build in single player (i could be mistaken though)
O heat, dry up my brains! Tears seven times salt
Burn out the sense and virtue of mine eyes!
To get epic spells you must be an epic caster (not just an epic character). Your character is epic if your level is greater than 20. You become an epic caster once you become epic in a spellcasting class.
True, it seems bio did put an extra check in for epic spells. It's a minimum of 15 PM, by the way.
If you tilt your head far enough and squint hard enough, anything becomes as simple or complex as you'd like--regardless of whether it is or not. -- A lesson learned from Stephen Wolfram's A New Kind of Science
I think that all this mess is easy to solve if you make a quest that a character needs to do when he is max lvl and that gives a great non drop item. But it gives it only to a pure class. Simple and straight forward. Given that item is good enough people wit try to stay pure class, but playing a multiclass will still possible knowing that you won't get that item. Simple as that!