Thread:Stray Bird/@comment-28048698-20170613021249/@comment-27971189-20170725130152

Not really.

EMIYA's Arm is case of human - Servant. It is difficult that you can say the only reason it could fit is because EMIYA and Shirou actually same person.

Siegfried's heart is case of homunculus - Servant. Compare to EMIYA's case the difficulty is lower, especially if the homunculus quality is high. Sieg quality can be considered high compare to other mindless homunculus in Yggdmillenia faction, although not on same level as Einzbern's as Einzbern's are able to keep the quality of all aspects to be high while Sieg created with intentional physical defect for his top-class magic circuit.

Its not far-fetched, its simply Higashide taking note from Illya capabilities to became a Grail that, by logic, could also means a homunculus can became 'container' for Servant as well.