Too Funny! - For years, I've been calling the product "Screenings" because that's what it's called up here in the great white north, then, after coming here and getting nothing but ????? when I said screenings, it was translated to "Crusher run" - the typical american term for it, now, we're back to "screenings".
Anyways, "smaller than gravel" stuff really laid down well.
Is your whole pool getting burried by 3 feet all around - it does not look like it.... it looks like only 1/2 of the perimeter will be burried and unless it's about 3 feet of backfill, it'll be within reach of frost.
If that's the case, then your pool will be under some really weird stresses - half being "protected from" and the other half being "subjected to" frost......

All these pools will say "do not bury" because they are not designed to be ingrounds, however, I have seen many AG pools burried to some degree (after filling) and unless you empty it, it's usually ok - frost however, could be a problem....
You may want to consider something other than clay as your backfill to help with drainage around and away from the pool....


Would it be at all possible for you to hold the dirt back using a retaining wall of sorts, maybe 4 feet back from the pool? I've seen that done many times as an alternative to burrying.

Either way - burrying or backfilling, I would highly recommend a bit of drainage around the pool, some "Big-O" burried in a ditch around the perimeter with a drainage tail on the low end ending up in some sort of subterrainean gravel distribution bed or even surface draining on the low end.........

get back with some more details please on actual burrying specs...