Wasn't this demonstrated by the Royal Chemical Society that pouring the milk into the tea creates a detectable trace of caramelization of the milk sugar or protein denaturation due to the momentary high temperature on the milk while the tea:milk ratio was very high at the initial pour? https://www.vahdam.com/blogs/tea-us/milk-first-or-last-the-s...
I was alway told the milk-last 'scalds' the milk, and I do prefer the taste of milk-first, especially with the first pour of the pot.
If making teabag tea, it's better to let the tea brew (and cool) for a few minutes before adding milk. Adding the milk just after the water gives a terrible cup.