TSMC reportedly holding roughly $1 billion of finished A20 Pro wafers that cannot be packaged because the DRAM they must be integrated with has not yet arrivedThe bottleneck exists because Apple moved the A20 Pro to TSMC's WMCM packaging, which bonds processor and memory at the wafer level, removing the option of stockpiling finished dies and adding memory laterThe launch is not expected to slip but could mean that post-launch inventory could be dicey, with thin stock and extended delivery estimates the likely outcome for Apple's upcoming devicesAround a billion dollars of finished Apple silicon is reportedly sitting at TSMC…