By this logic every single company on the planet would be a single-product company. The reality is that companies expand their offerings all the time – despite the cost, complexity, and risk of doing so.

A great time to expand your offerings is when there's an adjacent offering that's producing outsized returns for someone else, is easily replicable, and which you have an asymmetric advantage on.

I think everyone knows that when someone says "it's trivial" for a business to do something, it doesn't mean it's actually trivial. Doing anything of any value anywhere is non-trivial. It's shorthand for "doing Activity X is almost certainly achievable with an acceptable outlay of risk for Business Y."