Yes, when it comes to anonymizing a source, releasing no information is always better than releasing any information, even if that information is a mix of truths and falsehoods. But, releasing a mix of truths and falsehoods or less specific/more generalized truths can only be equally as bad as releasing all specific truths, but it may turn out to be much better. Saying your tenure was September 2016-August 2017 might match 20 people at the company, one of which is your source. Fudging your tenure to August 2016-September 2017 might match 20 people, but not your source. Saying your tenure was 2016-2017 might match 1000+ people, including your source.

There are trade offs in all of these methods, but I don't see them as being particularly wrong if you want to provide color to your story without materially affecting it, and can be confident that you aren't helping to identify your source.

While maybe not particularly valuable, it is pertinent when saying "x is worse in place y than in the military": without experience in the military, it would be impossible to say (not saying the words, but for credibility).

If you have a beef with this person, and set it up so your statements seem like they are coming from them, then you are playing with fire. If the person is very adamant that they weren't the leaker, the next question might be "well, who could leak and have a motivation to make their details look like this person's?", which may point to you.

If it is just a coincidence that the details of your fudging match a specific person, then they can still deny it. I don't know, but the point of all this is to protect a source, not to protect a random person who might be implicated by bad luck and punished illegally by bad actors.