As you said conflicting information... that is the thing about research (being on myself) you can often target the direction of the work to kind of get it to say what you want to prove... most people start from a point of "I want to prove this, I 90% believe it so I will find information to prove it more - where as the best way to be "objective" is to read 3-4 times more information that "disproves" what you want to prove.
that we are the only "animal" that keeps on drinking milk when we are grown up.
We are also the only "animal" that cooks/processes our food before we eat it, we are also the only "animal" that offers a processed form of milk to new borns, in the past if they didn't have breast milk, they didn't survive, but now more than 50% of babies are on Formula before 3months in many countries. We are also the only animal that uses other than ourself for transport... I think that "theory" is kind of a mute point given the evolution of humans IFYKWIM
In terms of milk, having worked in Immunology research, one researcher I knew believes (but can't get funding to prove) that one of the big issues with Diary intolerance is second & third generations... ie the sins of our parents & grandparents. If (like me) your parents were fed milk as a 2month old & then you were given milk (unprocessed not formula in the 30's & 60's) then one school of thought is that MPI is more likely in your children... DS1 was EBF to 4months & then had some formula from then & trialled cows milk at 13mo - big issues, ok with moderate amounts at 18mo. (he has confirmed low level dairy allergy - doesn't drink milk but has limited processed dairy) DS2 was EBF to 6mo (then solids) & no dairy until 11mo & no milk until 18mo - no allergy issues. So for me I do question the Formula (milk based) earlier in DS1's life was part of the issue. Also we really don't know how much a 'non- hypoallergenic' formula will impact with allergy either in future generations?? & even if it is cows milk in a mature gut that is the issue. With so many changes in food processing & diet over the last 2-3 generations it is getting harder & harder to know the impacts of other milks too.
One of the reasons Dairy is recommended in the diet is how much it provides in terms of one food/drink unit. The thing about rice/oat/almond milk is they need to be fortified etc to make them as nutrionally balanced as cows milk & we really don't have the long term knowledge as how they impact us, so while short term we know that there are less allergies with it how do we know how it impacts later... the level of processing bothers me as I like l-2 degress of separation to nature.
Given I don't really have a lot of dairy & nor does DS1 we have always looked at the balance of food groups. When Ds1 stopped BF at 13mo he didn't have a bedtime bottle or really any milk as a "drink" in the way I know lots of people give milk, I made sure he had lots of calcium rich foods as part of his diet, he did have formula on his cereal, but we didn't make milk a "drink" it was dairy part of other foods. If that makes sense.