It's used the two weeks waiting to start PCT for the same reason you've seen other methods of blasting it during that time only (without using during cycle). Stimulating the leydig cells during this period can help promote a quicker recovery. I personally like doubling my 250iu/week i use on cycle to 500iu/week during that two week timeframe but I wouldn't say it's necessary. A wise man once told me it's better to use hcg than to not. We stop using once we start PCT as hcg is suppressive. Hope this clears it up!