Question regarding bolt fixing.

I've seen a few posts recently where people are critiquing decks where beams are bolted to the side of a post, rather than sitting on top of a post.

I would have thought the shear strength of an M12 or M16 grade 8.8 bolt would be more than enough?

An M16 grade 8.8 bolt has a shear strength of 480MPA, which is a force of 75 kN, or 7,500kg.

Not to mention the friction between the beam and post from the compressive force of the bolts squeezing the timber pieces together.

So where does the concern come from?