/wp-json/wp/v2/blocks to request all blocks on the frontend, but I just get a response of
 even though I've made a reusable block in admin.
I suspect that what I mean by block and what Wordpress 6 means are different things, but I've not found the REST API documentation helpful in this regard - perhaps I'm too deep for definitions to be provided.
Why I'm doing this
In WP6, there are reusable blocks. These seem ideal to be pulled down via AJAX so that pages can be otherwise statically cached. Perhaps there's a better way to handle FPC hole-punching but I've not found it, and with a JSON REST API this seems ideal.