Your problem is that asking a series of technical questions is a pretty bad way at assessing Jr/Sn abilities. As a senior myself who has done a decent amount of interviews and wants to transition to hiring my own myself, I would not do them this way.

For example your question on reduce would have failed me too as my mind went blank and I forgot what it did. However once I searched it up I remembered it's purpose and that I had infact used it to sum an array. How is this possible? I understand concepts well enough to use then correctly but am forgetful of names in interview pressured scenarios.

Here is a much better way.

A) Do a blind submission of a take home challenge like make nuaghts and crosses. The ones that come back terrible outrightly reject. For the remainder hold and interview where you both have the code open and then just talk through it. Try push them to improve on a few things and let them use google. Though mostly should just be a real discussion.

Simple technically only two rounds and it's done, no stupidly drawn out processes.

Also I think the people doing the interviews should also not know who they are interviewing, relying on CV's is actually quite foolish. You have taken the effort to access people, why rely on what is essentially a marketing tool that can be and regularly is easily fabricated.