The post explains that One was considered as a new member of WINNER when Nam Taehyun left the group. This was something potentially fatal to WINNER since Taehyun was one of the two main vocals.
YG Entertainment considered recruiting One into WINNER because he had won second place in 'Show Me the Money 4' back in 2015. He had also already know Minho from the group through the show.
Ultimately, One did not join WINNER but made a debut as a solo artist and WINNER continued on as being a four-member group. He eventually left YG Entertainment last year in July 2019.
There are different opinions from netizens on this matter. Some say that WINNER is perfect as a four-member group while some say that it would have been nice it One had joined.
"WINNER is doing fine with their four members. I don't think another new member would have been a good move."
"One fits so well in the group. would have been nice to see him perform with them."
"One's so good looking though."
"I don't think One would have joined as a vocal so that's the end of that."
"Hmmm, their image fits well together."