My Google account is more than 18 years old and I hit an age prompt when I was trying to watch some FPGA video (out of all things). So no, account age is not necessarily a factor.
They probably need to account for parents allowing kids to use their account, so account age can be a factor but not an automatic pass.
Can't allow any underage synthesis.
Yeah, they could/*should* infer your age just by the fact you're watching an FPGA video
Field programmable gatorade is an adult-only beverage.