Playgrounds are fun, and I've done a huge amount of learning in them (and building them for my own play).
I'm not convinced that they develop great foundational knowledge about a system; they tend to favor quick, narrow dives (to any depth), rather than mucking around in all the boring bits that actually make the whole system. Great for getting the gears turning and keeping interest levels up, not great for full comprehension.
I'm not convinced that they develop great foundational knowledge about a system; they tend to favor quick, narrow dives (to any depth), rather than mucking around in all the boring bits that actually make the whole system. Great for getting the gears turning and keeping interest levels up, not great for full comprehension.