From one of the founders:
The actual task details are in the file contents, which aren’t read by bases.
https://forum.obsidian.md/t/bases-file-tasks-property/102375/5
I have moved my tasks to YAML so that they can be read by Bases, with each task being its own note. Super fast and configurable, and easy to embed where needed. And it saves Bases having to read the entire contents of notes, which as we have seen with the likes of Dataview only serves to slow vaults down. Unless there is a fabulously efficient way of reading old-style tasks, I hope the developers don’t change the code that works so well. If users want to use old-style tasks, existing plugins (and perhaps new plugins) already serve those needs.