In quick succession we were offered a variety of appetizers to us before we ordered anything. Thought they had the wrong table but after the third offer realized it might be their way of upselling? Is this normal?

That's how dim sum works. They will bring you options and charge you for what you take. You can eat this way solely, or you can order from the menu.

Dim Sum is where they make a variety of small dishes usually different kinds of dumplings and cakes, load them up on a cart and then proceed to go around table to table. If you see something you like then you choose that plate. The waitress will put it on your table and mark your card. Where you will pay for at the end. These small plates are usually shared. It's a good way of tasting a variety of dishes without the commitment of having to finish a whole meal. It's traditionally served weekends in the morning but sometimes other times. These dishes aren't usually on the menu. It's best to drink hot tea because it helps with digestion. So you can go in and eat this way or order from the menu.

If you were their for lunch around noon and mid day then yes. Its their dim sum hour. Their not up selling you it's just dim sum

When my family and I go to Purple Dot. This is the only way we eat. Dim sum Style baby. no upselling here

Morning tea, just like in China. Never heard them say 'dim sum' though

Depending on day and time, Dim sum is offered this way. Can run you into bucks if all you wanted was a couple of choices off the menu instead.