I think it depends on:

A) how old the product is: Twitter during its first 5 years probaby had more work to do compared to Twitter after 15 years. I suspect that is why they were able to get rid of so many developers.

B) The industry: many b2c / ecommerce businesses are straightforward and don't have an endless need for new features. This is different than more deep tech companies

There’s a third one, and it’s non-tech companies or companies for whom software is not a core product. They only make in-house tooling, ERP extensions, etc. Similar to your Twitter example, once the ERP or whatever is “done” there’s not much more work to do outside of updating for tax & legal changes, or if the business launches new products, opens a new location, etc.

I’ve built several of such tools where I work. We don’t even have a dev team, it’s just IT Ops, and all of what I’ve built is effectively “done” software unless the business changes.

I suspect there’s a lot of that out there in the world.