You should give the paper a more careful read, it discusses all that.
The control group was typical use, whatever the staff chose to do, which included not using masks at all.
The use of masks in the control group was about 23%! And that included medical, N95 and possibly cloth masks as well. Whatever they would typically use.
Here is their conclusion:
"Given the obligations to HCW (Healthcare Workers) occupational health and safety, it is important to consider the potential risk of using cloth masks."
The control group was typical use, whatever the staff chose to do, which included not using masks at all.
The use of masks in the control group was about 23%! And that included medical, N95 and possibly cloth masks as well. Whatever they would typically use.
Here is their conclusion:
"Given the obligations to HCW (Healthcare Workers) occupational health and safety, it is important to consider the potential risk of using cloth masks."