Seems to be intentional, honestly. Germinate Invoker Barbarian is clearly meant to be able to use abilities that require patience or concentration.
Enlightened Bloodrager is similarly construed to permit the user to use any spell, not just Bloodrager spells.
Other ways to cast spells while raging (aside from Moment of Clarity or casting as a Bloodrager) include the
Mad Magic feat (which requires bloodrage or moment of clarity rage power), the 1st-level bloodline power of the
Vestige bloodrager bloodline (uses a swift and halves morale bonuses, can also be obtained with the
Raging Blood feat), and
Furious Spell metamagic, which gives a +1 level penalty and a +2 to CL checks. This of course means that it is also possible to use a metamagic rod of furious spell to cast spells while raging.
Lastly, it is also possible to equip the
Robes of Xin-Bakrakhan, which is a ludicrously expensive item (198k gp) giving +1 to caster level, a +5 shield bonus (a +5 mithral buckler is cheaper), and 24 spell resistance in addition to immunity to calm emotions and the ability to use all skills and abilities that require patience or concentration when under the effect of a rage spell or similar effect.