They are lying.

Dovetails were invented by the Ancient Egyptians, the Pyramids are still here.

Given a choice, choose dovetails. Dadoes do work fine, but dovetails are better, presuming good fabrication.

While dovetails certainly are a stronger joint, they're overkill in regular drawers. I might see a point for very large drawers with heavy loads, like pot drawers. But otherwise if dadoes are significantly cheaper that's what I'd go with.

Dovetails are very pretty though. If you're the type to admire joinery whenever you open a drawer (I certainly am) then that's another benefit.

I have no idea what vinyl plywood is. I'd be a little more concerned about that than dadoes vs dovetails.

Yes dovetails are overkill. No dadoes in plywood are not as good and definitely not better.
Doweled or biscuit joints in solid wood can be as good, maybe a drawer box jpint (but Inever liked that)
Dovetails main advantage was when drawer bottoms were solid wood, which would eventually split. The mechanical advantage of the dovetail allowed the use of reversible glues like hide and fish glue. They didn't have aliphatic resin. Witht he advent of plywood bottoms and modern adhesives the mechanical advantage is not really needed.
Still with current tooling it may just be the easiest way to make adrawer box, especially with thicker material.
Nice delicate boxes, or those made from. Ply are better done with finger joints.

Whenever I tug out some of my retro bathroom drawers with wooden slides, I think that dovetails are overkill when you have good hardware. With good modern drawer slides I think any type of joint would be okay.

Dovetails do DO, however, tend to not be found in lower quality (American) cabinets. So, in other words, if you're looking at a cabinet line that doesn't do dovetails, it's probably a cheapie. (European style cabinets are a different ball of wax.)