So abt. 50000 DWT, or abt. 30000 GT?
20 crew would be abt. international standard for a tanker of this type and size, I believe. (Although an extra 3rd Mate would be unusual)
That is abt. double the size of ATBs used on the Alaska trade according to this:
A 25000 DWT tanker would not have any less crew than a 50000 DWT one in normal operation by international standard.
As long as it is allowed to operate an ATB with half, or less, crew I can see it is attractive to Owners/Charterers, but I cannot see how it is allowed by authorities and underwriter.
4 men crew on a small (<5000 bbls.) coastal tanker in Norway does look small, though, even if equipped with all kinds of bells and whistles.