Not true. I had buddies that dropped and went back to RS. They were for family emergnecies, but none the less, they dropped. I had seen soliders also dropped from BAC and went back also.
They did not voluntary withdraw. You can not voluntary withdraw from either and ever hope to go back. In fact if a soldier is thinking of VW at Ranger School, they will bring them for a night, let them get a hot meal and a shower before they make the final decision. The RIs will let them think about it and most of the time they will change their minds about being a VW. If you do not believe me go ask someone with a Tab. Same thing with BAC, if you VW no coming back. When I went I was in an airborne unit at Bragg and there would be no way in hell I was coming back w/o my wings. Same with guys that are from BN. you better come back from RS with your tab or face hell unless you medicaled.