Bay joins need rubbing down for definit in large rooms especially when working on your own . Say a room 200m + no way u can do that without getting bay marks
Even 50-100 m rooms on a hot day will make bay joins especially like neilydun said sometimes you cant use top end stuff . So the bog standard trade drys quickly . I was just speaking metaphorically when i said 200 msq. Just meant a big room. Screeding it on your own .
I wouldn't screed a big room on my own need at least 1 to mix ! About 30m2 is my max on my own but I'd mix in three tubs 2 in each one after the other so it's all ready to pour ! If its to hot screed late after noon or evening or shade windows ect..