Does Invisible Spell gör kallade varelser osynliga?

Jag söker en förtydligande för min grupp om Invisible Spell-prestationen från CityScape om hur det interagerar med Summon Monster (specifikt Summon Undead).

Boken anger:

You can modify any spell you cast so that it carries no visual manifestation. All other aspects of the spell, including range, area, targets, and damage remain the same. Note that this feat has no bearing on any components required to cast the enhanced spell, so the spell's source might still be apparent, depending on the situation, despite its effects being unseen. For example, fireball cast by someone with this feat could be made invisible in the moment of its detonation, but everyone in the area would still feel the full effect (including the heat), and any flammable materials ignited by the explosion would still burn visibly with nonmagical fire. Those with detect magic, see invisibility, or true seeing spells or effects active at the time of the casting will see whatever visual manifestations typically accompany the spell.

Med tanke på det skulle det göra den uppkallade varelsen osynlig eller mårligt den magi som omger uppmaningen att kalla in osynliga (och därför vara värdelös)?

Om varelsen skulle den här osynligheten fungera som regelbunden osynlighet eller större osynlighet, vilket betyder att om den uppmanade varelsen går osynlig, skulle den återkomma när den gör en attack?