yah, i saw some reviews got say seller dun provide installation n flashing. but if they do, surely get more business.
AFAIK, the staff are from China, so they are tasked to pack and give the phone to customers only. They will only ensure that the chinese ROM will have playstore inside, for most stores.
They aint interested in helping u coz they are not paid to do so. Business comes from the low price set in Qoo10, not the staff helping to flash ROMs though.
At least from my experience in buying 2 xiaomi export sets from 2 different stores in SLS. But it is quite easy to google the steps and follow.