I think milk always tastes different when you heat so much. The regular milk has good bacteria’s they help to relieve the upset stomach. We always need good bacteria for milk.

The meaning of drinking milk will be different if you use cold milk a little bit pasteurization or 100%.
The milk always have good bacteria according to the Wiki,” UHT stands for Ultra High-Temperature Pasteurization (also referred to as Ultra Pasteurization or UP) and means that milk is heated to about 280 degrees F for 2 seconds, which kills more bacteria (both good and bad) than traditional pasteurization, therefore, giving the milk a much longer shelf life before it spoils.
UHT milk packaged in a very very clean container, if not opened, has a typical unrefrigerated shelf life of six to nine months. In contrast, HTST pasteurized milk has a shelf life of about two weeks from processing, or about one week from being put on sale”.

https://en.wikipedia.org/wiki/Ultra-high-temperature_processing

https://www.quora.com/Why-don-t-Starbucks-drinks-with-milk-in-them-require-refrigeration/answer/Adrien-Lucas-Ecoffet?

https://www.100daysofrealfood.com/uht-why-some-milk-is-not-refrigerated/