Garlic usually does not make seeds. It tends to make little bulbils instead-- you can plant them just like miniature garlic bulbs and over the next few years they will grow into tiny garlic plants, then bigger ones, and eventually fully sized ones.
As regards garlic making hardly any bulb to speak of: I've left the scapes on, and still gotten reasonable sized bulbs.
It would be easy enough to test. Leave the scapes on just one or two, and compare bulb sizes at harvest time. It may be something that varies from one climate to another, which would explain why some people say it is important to cut off the scapes and some say it doesn't matter: each one could be correct for their own growing conditions.