Do the Twins draft/sign more high school and international players than other organizations? That would skew the numbers up for time of service. Do the Twins stick longer with pitchers trying to make them starters before deciding to make them relievers? Those are factors that could make your numbers meaningless.
The study was over 10 years, not just a year or two, and the end conclusion agrees with what many respected sites such as BP, Fangraphs, etc. have commented on from time to time which is that the Twins are slow to promote players.If you want to argue with facts feel free, but in this case the facts are what they are. Yes, the items you mention could impact how long a guy is in the minors, but the fact remains guys stay in the minors longer with the Twins than any other team in the league and it's not even close. Other teams also draft high schooler's etc.
Like I mentioned, we can argue if it's a good thing or a bad thing, but it's still a thing, and seems like a strange thing to try and twist or debate. If all you want to do is sit here and say the Twins organization is always right and never makes a mistake, I wonder why you bother responding to a thread that asks questions such asthis? Seems your mind is already made up, even when statistical reality is presented to you.
Further if you think the reason is the Twins draft more young or international players, how about showing some evidence to that fact. Otherwise, hard to say the article I referred to is meaningless. You could do that with ANY statistic, Mauer hit .300 last year, yea but maybe he only faced lousy pitchers, must be a meaningless stat since you didn't compare every pitcher he faced to the rest of what every hitter faced, see where this goes?