There seem to be a few misconceptions about Spin Velocity, specifically in regards to Attack.

A higher Spin Velocity does not necessarily equal a more powerful attack. If this were true Wide Defense would be useless. Spin Velocity and Rotational Velocity are different things. Spin Velocity constitutes the amount of revolutions per unit time. Rotational Velocity is the linear speed component of a given point on a rotating body at a given instant. Spin Velocity creates Rotational Velocity, and Rotational Velocity is what creates Rotational Inertia, which is what assists in Attack (given a point on the perimeter of the spinning body. Spin Velocity can up Rotational Velocity (MF/HMC), though to do so in Beyblade is less efficient than upping your Rotational Inertia through outside focused weight. This is why we use Wide Defense instead of 10 Heavy in Attack customizations, because Rotational Inertia is the force behind an Attack (Rotational Inertia is a combination of Rotational Velocity and Mass).

Real world example: Spin a ball or a coin or virtually anything. It will complete vastly more revolutions per unit time than the Earth does, but the perimeter of the Earth is moving much faster (1037.5646 mph/1669.8 kph). Would you rather get hit with a beam moving at that speed or the speed of the perimeter of your ball? Yeah. Obvious answer. That’s Rotational Velocity. The force behind the hit is increased with outside-focused weight, so the wider and heavier (on the perimeter) the better.

In the Defense section of that article it notes a pro as being: "A faster spinning Beyblade will hold its ground more effectively when struck by the opposing Beyblade." (wait then why launch WB at 80%? Oh yeah, because this is wrong), then it later mentions as a con: "Defense-type customizations will be easier to move if their parts are built for high spin velocity." Seems like a bit of a contradiction.

Survival note: Rotational Inertia allows you to retain spin, not Spin Velocity. That's why most good Stamina Metal Wheels are fairly wide, and partially why MF's suck for Stamina.

In the realm of Attack, Spin Velocity is never a bad thing, but never should Rotational Inertia be forgone in its sake (why HMC is fine and 10 Heavy isn't). No wonder people found the best Plastic Attack combos to use either Wide Defense and Full Auto Clutch or Wide Defense and HMC. Same with Defense using Wide Defense and SG Bearing Version 2 or Wide Defense and HMC.

tl;dr Spin Velocity makes you complete more spins Rotational Inertia makes your Attack and Defense Better (your perimeter moves faster and you're harder to flip).

EDIT: I chopped this up and moved stuff around so now it sounds awkward, I'll fix it later.
Why were people launching WB at 80%? Also, I agree
that the defense section on that article is off. If you go to the article about defense types, none of the reccomended combos have their weight completely focused in the center. I think it's a misconception that defense types must have high spin velocity, when instead it's that defense types (at least those based on weight) tend to have higher spin velocity because they are heavier.
Also, I don't recall Full Auto Clutch being preferred.
Full Auto Clutch is the most used option after things like SG Metal Flat 2, Storm Grip Base, Grip Base, and SG Grip Change (except no one used it).