Introduction
Warning: Contains spoilers to the Harry Potter series.
One of the most notable parts of the Harry Potter series is that Harry might have ended up dead at the end of book 7, as Snape notes in his conversation with Dumbledore. Dumbledore kept Harry alive "to be sacrificed at the right moment".
Now Harry Potter looks up to Dumbledore who is the strongest wizard in the world at the time and who at a glance, seems to be the perfect mentor. One could argue that it is an honor to be in the presence of such a highly esteemed wizard.
Meanwhile, Harry is kept in the dark, and especially since book 5 (Where the whole Dumbledore's army shenanigans happens).
It's important to note when such a situation occurs. If you are not being given critical details that affect your career, somebody is playing you. The advice to have 6 months in living costs saved in your bank account is a good one, especially in the IT industry.
Mushroom management
Dumbledore management is a more benevolent form of Mushroom management ("Feed them shit and keep them in the dark"). There might be genuine kinship, mentorship, and care with Dumbledore management. But the fact of the matter remains: you are not being trusted with critical information that affects your career. If you are in a situation like this, it's worth figuring out what kind of margin of safety you have. Unlike Harry, there's no plot armor to protect you from the consequences.
Should you be negative towards Dumbledore?
It is generally a good idea to always be working hard (if you are healthy and have high levels of energy). The fact remains that as long as the relationship remains cordial things should go well, and some things are above your paygrade. However, things might degenerate once Dumbledore dies (or finds another job).
Legitimate reasons to withhold information
There aren't any. If it affects your career, your manager is a coward for not telling you. From the workers side, it is advisable to cultivate apathy instead of anger. For some reason, HR prefers apathy over anger. I could make the argument that apathy leads to lower productivity, but it seems that corporate environments can survive (and might prefer) you working less intensely.
Dumbledore might also be lazy or autistic. You never know in the end; some managers don't understand what is being said (language barrier) don't speak the corporate language of euphemisms, etc. In the end perhaps the shocking part of books 6 and 7 in the Harry Potter series is that Dumbledore is inevitably human with human shortcomings. His brother isn't very fond of him; and his sister suffered (and died) despite all of Dumbledore's genius.
Perhaps the most important thing to learn is that Dumbledore is a crutch and there is no one to save you from the reality of corporate idiocy, but that's too metaphysical.
The fact of the matter is that you have to follow orders from Dumbledore. While under his command, it's important to not end up blindsided.
In general, serving under Dumbledore is not a problem until the day you have to face the facts on your own.