People however don't tend to have perfectly uniform cups even in their own home, and whenever outside one's home, the chances are very low that somebody can make accurate adjustments for a new vessel due to our well documented inability to compare volumes across different vessels.

Further the milk first method cannot account for differences in tea strength across brewings.

If we take the amount of times/chances milk first could lead you astray vs. the amount of times tea first plus stirring as you pour could lead you astray, the former is oviously greater and more likely.

I saw somewhere here somebody talking about the different ways the milk sugars might caramelise with the two methods being a factor, and obviously the article suggests there is a difference between the two methods in terms of flavour, but in terms of reliability of flavour, the latter option is obviously more reliable.

I take my tea black and unsweetened anyway, unless I'm drinking Hong Kong style milk-tea that is... then all bets on my blood-sugar levels are off...