Do you have a page reference on that?
From SRD:
it is under the psion description (same place in the book - pg 20) - but the book is written such that a lot of information that applies to every psionic class is placed under the psion - like for instance the astral construct information.
Armor does not, however, interfere with the manifestation of powers.
Combine that with the following (pg 53)
He has no need for messy material components, verbal cues or awkward gestures.
and from the PHB
Nonproficient with Armor Worn: A character who wears armor
and/or uses a shield with which he or she is not proficient takes the
armor’s (and/or shields’s) armor check penalty on attack rolls and on
all Strength-based and Dexterity-based ability and skill checks. The
penalty for nonproficiency with armor stacks with the penalty for
nonprofiency with shields.
IMO the "targeting" is part of the manifesting/casting and not a separate issue it is just resolved via the "attack" method. Otherwise you end up with situations like generating AoO when making a ranged touch attack when casting a spell (or manifesting) in addition to the one generated by casting/manifesting.
And the armor penalty is based un using Str or Dex to make an attack - a power doesn't really rely on that since there are no gestures involved and it purely mental - although it requires concentration which is why concentration checks are required when grappled and the like - although you can always attempt to manifest a power when grappled (only spells without material/somatic components can be attempted).