Why do Gerber Graduates teething biscuits and crackers say they are for toddlers only?

All the development books, articles, etc say that babies should be able to feed themselves a cracker by 7 months, but all the baby crackers (Gerber Graduates, etc) say they are for crawlers and toddlers only. My son is 7 months today and can't crawl, but he certainly seems able to feed himself a cracker! Are these things safe for him if I let him eat them only in his high chair and supervise him? Thanks!