My guess is you already have a gut-feeling about how the company views taking time off.
During holiday seasons, many managers will try and coordinate future time off, so there is ample coverage. If that was your boss's goal, I think there are a few flaws and possible reasons to believe there is something else going on.
Calendar of the past month - There is no point in showing who took off three weeks ago. The calendar should be for future scheduling. People may want to coordinate vacations and see if they can switch with someone else.
Vacation Days Left - If you ask people to take personal time off in advance, you can have a future calendar, so knowing who has more time left, shouldn't be a critical piece of information. A day here or there shouldn't require a lot of advanced notice for coverage (There are some fields that are critical.). What type of day off (medical/personal v vacation) shouldn't matter. Either someone is missing and adjustments need to be made or they don't. Otherwise, it's really not much help. Everyone just needs to do their part in the planning. Indicating anything "medical" is really a bad practice and is getting into health privacy areas.
You're more likely to see other indicators that time off is being viewed negatively. People will make snarky comments when you come back. There are too many restrictions and a lengthy advanced notice periods that make it difficult. The boss will ask for ways to contact you when you're gone. You're expected to answer email and phone calls because they think it is an emergency.
When you feel uncomfortable asking for time off, you'll have your answer.