Your A grade description is pretty much mine too.For me:
A grade is probably a combination of north orientation, tree lined street, quiet but sufficiently close to the heart of a suburb, beautiful nature strips, beautiful houses next to or opposite you, could be regarded as a top 5 street or top 2 pocket in a suburb, ideally good bones, best if it holds development potential, no undesirable buildings or industrial land visible or probably even too close by, close to key public transport infrastructure.
I guess a B grade is a property that doesn't exhibit enough of these attributes. Particular killers for me would be main roads, opposite commission flats, T intersections, street looks ugly or is too narrow, street too industrial and doesn't have enough trees or has ugly nature strips, it belongs in a dodgy pocket of a suburb or an inferior pocket, far from the shopping strip, far from bus/monorail/tram/train.
I would never/haven't ever entertain the idea of buying a B grader.
I think everyone (investors) should follow that A grade selection criteria - might cost a little bit more, but better in the longer term.