In any case, did Doshu and the other Hombu teachers indicate an acceptance that extant IP training continues via sources outside of the Aikikai (and/or has such a thing as sanctioned IP training expressly designed as a complement to kihon training internal to the Aikikai evolved, even if relatively clandestine and limited to individuals vs. being system wide)?
I think IP training within aikido got tangled up with the politics associated with the Koichi Tohei split. In fact, differences in opinion about how both aikido and ki/IP should be taught were the stated *reason* for the split.
The level of IP skills that Tohei Sensei did or did not have has been debated, but in the context of this discussion I'm not sure it matters. When he left the Aikikai, whatever skills he had went with him, *and* those who remained had a strong political incentive to discount everything he did.
Certainly it didn't help that Ueshiba Sensei himself never formalized this instruction, and so there wasn't an O Sensei-approved methodology to fall back on after he died.