There isn't any to consider the Compendium a rules source- it was set up and coded by an outside contractor, and often contains errors. Path of the Blade is a relatively well known one, but there are others. For example, it (and the online Character Builder) only give 2 of the traditions for hybrid monk, even though all of them are applicable. Another such example is the Order Adept theme, where the Compendium gets the level 5 feature completely wrong for PCs who don't have spellbooks (this too is reproduced in the Character Builder).
The Compendium is in error on Path of the Blade, because the original wording is quite confusing- do the two attacks listed on the upper part of the power consist of the primary and secondary attack, or do you make the primary attack twice and each one gets a secondary attack tacked on? The people coding the compendium tried to make sense of it, and changed the wording/format in accordance with their views.