8 week maltipoo with open fontanel

Hi I was informed that the 8 week old maltipoo puppy we are to adopt has an open fontanel. It is a toy maltipoo. The puppy does weigh slightly less than it’s litter mates but acts completely normal. It weighs 1.4oz and litter mates are around 2 lbs.
So in my reading online it says sometimes the fontanel takes longer to close and sometimes not at all. Does anyone have experience? Should I not adopt this puppy? Thanks