I see people in competitive telling me to give them the 2nd half and now I've seen it in pro play. Why do people fill it to half and then let a team mate defuse the 2nd half?

I think this crosshair looks cool, and it would go well with shotguns. Thanks in advance! I saw it on a youtube video and commented, asking what the crosshair is, but I haven't gotten a response. ​ https://preview.redd.it/vayldg05...