Given the low number of hth spec edges available (only two with this limitation). While thematically it can be argued to require "extra" dex, you could just as well say that it's simply part of the technique for these masters of evasion. I just feel the more choices for character customization there is the better, so care should be taken if/when creating any "artificial" edge obstacles for different builds...

By the way, can you discuss at level 1 before practicing anything and get the correct "You will never learn X", if applicable (to make sure you'll have the chance to check a specific edge)?