Parents in China do not trust local brands of baby formulae. There were tons of it tainted about 10 years ago that literally killed 1000’s of children.
In HK tourist are only allowed to take 2 cans of powdered formula back. Otherwise the mainlanders where buying out entire stores. They can sell it for 8 or 10 times the price if they have a receipt from HK.
Since the PLA pays really badly, the sailors were probably just taking it back to China to sell.
The captains are then permitting and facilitating their crew in being black marketeers and free market capitalist.
“In HK tourist are only allowed to take 2 cans of powdered formula back.”
I’ve seen some YouTube videos of people buying in HK and taking their purchases back to the PRC.
Within sight of the border guards they would hand their purchases over to the “collectors” who would pay them their cut. By end of day the collectors would end up with dozens of cases of baby formula and chocolate.
One video followed an older couple who went to three different stores, each buying their 2 cans of formula at each store. Probably a nice addition to their income.