I think any competent nation is able to obtain this type of information - but it will require doing some work. I feel the point is, why give the other parties information for free, where we could easily make them burn money to get it?

I'm thinking back to the Cold War - one way of seeing the rivalry between the US and USSR is as a game of making the other side spend more and more money, in hopes the enemy's economy will give out and collapse before yours does.

The known vulnerabilities of a tank (e.g. X% will be defeated by weapon Y in situation Z) will usually be classified higher than the operator manual (which however may contain technical or tactical work-arounds). E.g. the existence of a defensive aid suite on a tank system may be unclassified (because it is plainly visible in photographs), what it does may be restricted, how it does it may be secret and how well it does it may be top secret.

Excluding the IR that info would not be in the operators manual. Also, capabilities such as type of missile systems on the tank are in practice not secret and present in 3rd party catalogues.

The only real downside I can see of public manuals are the risk for adhoc use of captured equipement. However I believe the upside of having the operators being able to use the equipment properly easier is greater.