This is my view of the situation - without considering what was the medieval paradigm and how knowledge/mind/spirit was considered at the time.
"Exchange of the Two Minds" looks very much like a possession. Maybe the labelling of the spell suggests that it could be possible to transfer part of one mind ? However, in effect, it is a full-fledge possession. It is thematic. Metempsychosis is a thing.
"Exchange of the Two Minds" gets complicated because of the soul aspect since Hermetic magic is not supposed to touch it so it looks like the soul remains in the original body where the mind travels to the other one. But if you are willing to discreetly hide that under the rug, Exchange of the Two Minds has its place in the grimoire of hermetic magic: it is not only the knowledge, but everything that is shipped to another body.
There is no spell touching "Knowledge" as mechanical skill set. My take on that is the following: because of the mechanic of hermetic magic, as soon as a "little bit" is allowed within a specific aspect of a form, then it becomes very hard from a rule point to forbid bigger things. More specifically, if it is possible to temporary transfer some knowledge, it becomes hard to prevent more powerful spells to steal knowledge, transfer large portion of it, aggregate it, speed up its absorption, etc. And then, it becomes the "weapon race": start your apprenticeship as Mentem specialist, because that's all you will ever need, since you will "spell-in" any other knowledge. And of course, it leads to the question: why was is not done before ? Considering Guorna morality and attempt at possession, how did she not do it before ? And if the answer is because she missed some key element that Bonisagus theory would later fill, why nobody else afterwards did not research it ? It is not like if all mages were parangon of virtue and morality...
Sure, it is possible to design limits like Warping, accelerated aging, but it becomes additional rules set in place to kind of control an exponential problem.
And it is easy to see that it is already lurking nearby: if it is possible to read mind, create fake memory, etc... why specific memory cannot be transferred, shared, implanted ? Short of a hard, arbitrary rule mechanic "So far it has been impossible to do it", there is no other explanation.
I agree that it could lead to plenty of cool things: automaton becoming preceptor for new generation of apprentice, developping quirks. Dark stories of powerful spell-theft by dreamwalkers, etc. However, the downside of it, as soon as it becomes part of the spell guideline, the logical consequence becomes "very annoying" - instead of becoming tools for interesting stories, it completely changes the paradigm and offset the delicate balance that magic theory is so far.
There is plenty of discussion in this forum about power, maximum level of Summae, Art level of experts, why is the Order not more powerful that it is know, etc... but I believe (and it is purely a gut feel) that spells affecting knowledge have the most potential to degenerate and completely break a system that is already quite fragile.