Why not place a isolator after CDMA PA?

In general , place a isolator after PA in CDMA phone for protecting PA , while a PA vendor declare that it's no need that place a isolator after PA for his PA . Could u tell me why?

In a CDMA system the reason of the isolator after the PA is to have a stable ACPR vs VSWR.
The goal on these days is to design a CDMA PA, which doesn?t have bigger ACPR variation vs VSWR (usually 4:1).
If can?t meet this requirement have to put an isolator.
rgds