Is this rude or is it just me?

Kiddo (9) received a birthday party invitation today. It's a party for 3 siblings, because their birthdays are close together. I'm reading it and get to:

"Gifts are not necessary at all! But if you're anything like me, I always get a gift. I've added some gift ideas IN CASE you wanted to get one. Please do not feel obligated at all. "

I always buy a gift, but this really rubbed me the wrong way. Also, do I have to buy gifts for the siblings as well or just the kid that my kids knows?