It is. And you're right to be skeptical of such arguments.

But such arguments also happen all the time. For example, if you join a company as a junior developer, most people would trust an existing senior developer.

I was about to write "I think it's fine to mislead kids into thinking they can make money." Then I reconsidered.

After reconsidering, I think it's fine to mislead kids into thinking they can make money. Lemonade stands and lawnmowing for neighbors are examples of this. They may make a little bit, but unless they're exceptionally lucky, no one would be under any illusions that it would become their full time profession.

But he is CTO of a company trying to become Roblox which takes half the money from kids the article/video talks about, and he's CTO of a 30% app store which takes the other half of the money from kids the article/video talks about.

Why does his C-programming ability have more weight than his obvious conflict of interest weighing in here? He may be being geniune, but since he works in this exact area, it is too tainted by that to take at face value or especially to take on authority.

Lawnmowing for a neighbor takes about an hour and earns maybe $10. Making a Roblox game takes perhaps 100 hours and is almost certainly going to result in earning $0 for everyone except the Roblox Corporation.

Ditto for learning the violin. (In this case, you learn Lua.)

But is it okay for a company to mislead kids into thinking that learning the violin will make them money?

An argument from authority isn't inherently a fallacy, as your own wikipedia article mentions.

But, like you, I do think it is inherently a flag that suggests other inputs are necessary. And that all opinions that solely reference the authority are equally lower weighted until additional inputs are found to match, or further negate.