This type of question is OK, but will not be allowed to receive speculation, so you should consider strongly whether asking “what's the rationale for why it is this way?” will actually give you the answers you're looking for.
We can easily tell you what it does, and whether it really means you can do a specific thing, according to what the text there says. If you're wondering if it's supposed to do that, what you're going to be asking about here is the designer's intent: you want to know why they did what they did. This type of question is usually tagged designer-reasons.
Per multiple previous discussions, questions about a designer's intent, reasoning, etc, has only one acceptable type of answer: an answer that cites explicit designer statements demonstrating conclusively what they were thinking or what their intent or reasoning was, because they are saying so and we are quoting them saying so — or something very close to equally convincing. Answers not providing citation of this level get deleted.(note)
These rules exist because otherwise we get a lot of answers containing pure speculation on what somebody thinks the designer might have been thinking. Sometimes these answers also attempt to reverse engineer conclusions from some limited amount of related output in the game, but that doesn't make the speculation any more correct — it just means it now has truthiness. It's making guesses either way. Those answers aren't OK, and get removed.
The alternative to having these rules right now is that these questions just get closed as primarily opinion-based, since they just invite tons of opinion on “here's why I think things are this way” and then the question gets five different answers all providing different contradictory speculation on why things are this way, not all of which can be true and all of which have no conclusive evidence whatsoever.
The idea is that while certainly we cannot know what exactly was the developer thinking at the moment of writing the feature X, with both practical experience in using the feature and through quotes and talks with the developers we should, in principle, be able to get a pretty good approximation of the thought that was standing behind the design of the feature X.
The only kinds of answers that we'll accept are those that do know, and show you they know, because they are quoting the developer saying so. We won't accept answers that just try to get a sort of good approximation.
If there are no such quotes available, you may get no answers, or you may get speculation (which we'll delete).
Note: These special rules are frequently attributed to a magical attribute of the [designer-reasons] tag, that exist if and when that tag exists, but it's nothing to do with the tag. It's the class of questions that has these rules — that class of question just usually coexists with this tag. Tags don't apply rules, they just describe the content of the question.