They could do that just fine if they picked an existing UI library on a company level. There's no need to invent their own.

Never in the history of software has one lost a sale due to how the buttons of their product look like.

And I guarantee you that their internal library will be worse than popular options out there. The amount of time I've been in meetings where 10 smart, well-paid people from 10 different products in a company are endlessly discussing paddings on an input field... It's just a complete waste of time.