Those aren't viable seeds. Cavendish bananas (or other bananas that are cross-breeds) have 3 chromosomes (triploidy) since they are cross bread between a diploid (2) and a tetraploid (4). These triploidy cells cannot perform mitosis and thus do not enlarge in the banana. They still have "seeds" but they are so tiny that they pass right through our digestive track and don't break our teeth.
I do remember eating bananas where the seeds where all about 0.3 mm to 0.5 mm.