As far as I know and based on my experience, yes, that is true for both the WDW and DL 1/2 marathons. This past DL 1/2, once we got through Angel Stadium (mile 10), people started high fiving each other because they were "safe" from being swept. There was a bus around mile 11 in case you needed to drop out voluntarily, but no sign of sweepers anywhere!
However, you should be aware that they start dismantling the course and turning off clocks after the time it would take the last runner to cross the start to complete the course at a 16min/mile pace. But the finish line will be there waiting for you, and you will be allowed to get there under your own steam! Although I suspect that won't be an issue -- I find that once I hit the 10 mile mark and know there is *only* 3.1 miles between me and my medal, pace is less of an issue. In fact, I think thats why I saw several people go down between mile 10 and the finish line at
Disneyland -- it was too hot and people started to really push to get done knowing the finish was relatively close!
Erica