As you have yourself supplied part of the answer, it is obviously not. Besides it's geographical concentration, the other obvious facts are (1) the age of the haplogroup is obviously far older than Indo-European, and the main migration route was via Anatolia, not the Steppes unlike the R1a. (2) the R1b were in Western Europe much earlier than the R1a. They founded locally the Bell Beaker culture, which originated from the coasts of Iberia. (3) the people in Ibera, large areas of France and Northern Italy spoke non-IE languages right into historical times, only switching partially to Celtic, then almost fully to Romance languages in the days of the Roman empire. (4) Basque, which retains its old pre-IE language also have the highest concentration of Rib, and lowest for R1a. All the assumptions that R1b is IE does not hold water, in the face of these data. What we can, however, say is that R1a and R1b split nearly 20 thousand years ago, before IE existed. The languages they spoke also evolved independently. The R1b folks arrived in Western Europe, and replaced most populations except in Scandinavia and the Balkans, where they mixed with the local Germanic (I1) and the (I2) Balkan natives. The arrival of of the R1a from the Steppes later on led to the mixing of the R1a and R1b in central Europe to produce Celtic, an IE language with tantalising links to Basque. The colonization of large areas of Europe by the Celts resulted in widespread language replacement, though much of Ibera and France remained old pre-IE. Only the Roman conquests successfully converted these areas to IE speaking, with the exception of its last remnants in the Basque territories. It is pride and refusal to identify with the vanquished that led people to insist that R1b is IE.