Hello,
Variants are products in the database ; but they might not contain all information and when there are some "blanks", HikaShop can load the information from the parent product (also called "main product").
In the email, because you have access to the raw data, the information from the parent product is not directly available.
You can see to customize the email preload in order to process the data and copy what you need for the variant products ; the other solution is like you wrote, to also have the information in the variant product.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.