Hi,
Yes it is normal. In the HikaShop backend, it is the exact same thing.
If you want to apply a discount on several products, you have to apply the discount on a category.
You can create a category unpublished, which will be hidden for the rest of the store. This hidden category could contain your 3 products and if the discount is apply on it, it will be apply on your 3 products.
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.