Not a landing page, but something that will help me build it later on.

The equivalent of its title/subtitle and how I will answer the question "so what is XXX?".
I also try to figure out what follow-up questions people will have (which would be the landing FAQ)

I think Apple is supposed to start any project by writing its press release? I can't find where I read that.

Whether it's this or a landing page, it's a great practice. It forces you to focus on the essence of your value proposition, be clear in your mind about what job it fulfills.

Landing page hypothesis testing is something which helps a lot and I have seen from very small to top companies like Amazon using it to validate their product ideas. It definitely helps to start with a landing page having a wait-list to see how many people are actually interested.

This initial indication is really important and can save you a lot of development efforts, may help you come up with better solutions and even reshape your MVP.

I do prefer to start my projects with a landing page due to these benefits, if I haven't already validated the idea.