I think you missed the point, since your post has nothing whatsoever to do with what you quoted. The point was that after the war in Iraq started, foreign terrorists streamed into Iraq to fight against Americans. I actually consider that a positive thing.
Where did they come from?
Foreign terrorists streaming into Iraq most likely was a positive thing for Russia, as Russian casualties in Chechnya dropped about the same time that terrorist activity in Iraq started rising.
I admit that is far from convincing. Russian casualties in Chechnya were about 200 per month in 2000, and a little less than 500 per year in 2001 and 2002, so the tide was already turning in Chechnya. Then casualties dropped to under 300 for 2003, to under 200 for 2004 & 2005, to under 100 in 2006. Towards the end of 2004 was the Beslan schoolhouse massacre and was a turning point, in a way. After that, rebel leaders started dieing rather regularly.
But the increase in Iraq was pretty large if all of Iraq's terrorists were freshly trained. I think a significant portion of those folks had to come already trained from somewhere else. It might be a stretch to say terrorism in Iraq turned the tide in Chechnya. It's more likely that once the tide started turning in Chechnya, Iraq seemed like a more promising operating region.
In other words, terrorists flocking to Iraq didn't turn the tide in Chechnya, but it did make for a more rapid turn of events in Chechnya.
In the grand scheme of things, I don't think it mattered where terrorists fought. All that happened was the battle shifted from one country to another.
On a smaller scale, all that happened was that the US got the opportunity to fight them instead of the Russians fighting against them.