Some API documentation contain the info since which version of OOo or LO that function is available. Extension developers have to provide a "minimum version" that is required for that extension. Because the SINCE info is rarely given, it is simply impossible to know this min. requirement. Example: BorderLine2 (http://api.libreoffice.org/common/ref/com/sun/star/table/BorderLine2.html)
I'm going to bring this one up with the devs, I agree that it should be done, getting everyone on the same page can be difficult. This isn't so much an enhancement request as just a request for us to be more concise. I'm going to close the bug as INVALID only because it's not something that we can actually do one time but instead a methodology that we hope to achieve. Thanks for bringing this up, hopefully we can get everyone on the same page