Indridi Indridason's contact with Emil Jensen

Most researchers of mediumship regard the "spirit controls" not as spirits at all but expressions of the medium's unconscious mind. This is because almost never is there veridical information or other features to suggest the "controls" are spirits of deceased people but usually many things to suggest they are part of the medium's psychology. This contrasts with communicators that provide real evidence of being dead people.

Yes, but I want to add that many researchers of mediumship also thinks that the controls can be "overshadowed" by a real spirit. According to Gauld in Mediumship and Survival page 117-118:
"It would seem, therefore, that we have to abandon the idea that the controls of trance mediums are the spirits of deceased persons temporarily controlling a living body. Are we then forced to adopt some form of the super-ESP hypothesis, to suppose that Mrs Piper and Mrs Leonard were able to inject into their dramatic representations of various deceased persons correct and appropriate information obtained telepathically from the minds of living persons or clairvoyantly from existing records? Mrs Sidgwick did not think so. She eventually came to believe that behind Mrs Piper’s dramatic rendering of communication from the dead, overshadowing it and |118| somehow directing its course, there might sometimes lie those same deceased persons who figure as characters in the drama. The medium writes many of the speeches, and ensures continuity in the plot; but some of the lines (perhaps the most important ones) are filled in by outside authors. Let us call this theory the theory of ‘overshadowing’. It seems to be a version of it towards which William James moves at the end of his report on Mrs Piper’s Hodgson-control (74, p. 117):
Extraneous ‘wills to communicate’ may contribute to the results as well as a ‘will to personate’, and the two kinds of will may be distinct in entity, though capable of helping each other out. The will to communicate, in our present instance, would be, on the prima facie view of it, the will of Hodgson’s surviving spirit, and a natural way of representing the process would be to suppose the spirit to have found that by pressing, so to speak, against ‘the light’, it can make fragmentary gleams and flashes of what it wishes to say mix with the rubbish of the trance-talk on this side. The wills might thus strike up a sort of partnership and reinforce each other. It might even be that the ‘will to personate’ would be comparatively inert unless it were aroused to activity by the other will." https://www.esalen.org/ctr/mediumship
So the Jensen control, who was a part of Indridi's subconsciousness, can perhaps have been overshadowed by the real spirit Jensen.