There's an enormous gap in complexity, required skill, etc between creating these Scrappy applications and building the whole app in React, and then getting it deployed, complete with real time syncing, authorization (as they've implemented with their "frames" and everything. It's at least an order of magnitude greater in effort.
> software, unlike a meal or a home-made sweater, comes with an implicit support contract that lasts forever
I don't think it always has to. It tends to be that way because so far, the lift to create a functioning cross-device multi user application has been high enough that the economics of it requires centralized teams of specialists to build an application for many hundreds of people.
If you lower the stakes really low to the point where the app is as serious as a spreadsheet, then compare it to spreadsheets. Almost everyone has dozens of really casual spreadsheets, many households have shared google sheets for particular, short-lived or casual or constantly changing use-cases. When you slap together a spreadsheet with your partner, you aren't making a promise about long term support and compatibility with the spreadsheet.
Or an other similar thing would just be paper and pen and tape, up on a whiteboard. All kinds of little "hand made" "applications" like this exist in households and in offices. Kanban boards are an example of this but there's and endless different kinds of "board-based physical apps" like chore charts and weekly meal plans. When someone writes on their fridge a list of chores and starts tallying who does what, that is not an eternal promise to maintain the piece of paper with chores and tally marks protocol/system.
The comments about being a SAAS, walled garden, and about the specific implementation here wrt where data's stored etc, this is just a prototype. A POC.