There's a comment in the source code:
I had forgotten this rule (it had never mattered to me anyway):// Omit exactly one space or tab from the title criterion.
Before I found where that's documented, I read this:Criteria beyond the first should be separated from the previous with exactly one space or tab
When talking about a relation between two items, it is redundant to use the word "both" - and to me it sounds unnatural. It's not possible for only one to be separated by a space while the other isn't, unless the thing(s) they're being separated from aren't each other. Therefore, I tend to think that "both" implies a relation between each of the two items and a third unnamed item. In other words, it could be saying that the ahk_ keyword may be separated from the previous item by zero spaces, which is untrue. I suppose that simply removing "both" would be a sufficient fix.An ahk_ criterion always consists of an ahk_ keyword and its criterion value, both separated by zero or more spaces or tabs.
Source: WinTitle & Last Found Window | AutoHotkey v2
I think it would be worthwhile for the ahk_ section to mention the rule for separating ahk_ from any previous criteria, even though it is documented under Multiple Criteria.