I stand corrected, time has certainly made my recollections hazy. The critical thing here is that BTS and WWDC are not necessarily tied together.
And because someone will speculate, BTS is not viewed internally as an opportunity to "clear out old product." BTS is just part of the Company's normal operational rhythm.
Apple's internal focus on accurate forecasting and operational excellence is relentless, and rarely is there any excess inventory in need of disposal at a low price (Vision Pro inventories notwithstanding). Occasionally mild overages in inventory will be made available to selected resellers on a product-by-product, market-by-market basis via a deal desk process.