The reasoning I employ is based on the empirical evidence that is available at this time, as you parlayed: "discovered subclades" in the Near East thus far.
Data is only evidence if it sheds light on the question you want to answer. If the question is "where did R1b1b2 originate" then simply counting up the number of subclades you find in a particular location is not very informative, especially if you know that some important locations have simply not been searched at all.
There is not bulletproof method for identifying the origin of a clade, but one thing you might look for is diversity: where do you find the greatest haplotype variance? For R1b1b2, that appears to be the Near East.
Another thing you might look for is phylogenetic structure: where do you find more "early' branches relative to "late" branches? For R1b1b2, that appears to be the Near East.
A third thing you might look for is brother or cousin haplogroups: where do you think the origin point of paralllel clades might be? In this case, the origin point of R-M73 seems to be the Near East.
And so on.