It is pretty much certain that 19,900 coins were submitted to the TPGs. So I am 99.99% sure that the WF Hoard is that size.
If that was the first submission, then there could have been other coins (including non-Saints and maybe non-gold coins) that were secretly disbursed elsewhere though it would be difficult to submit a large hoard to the TPGs and keep it a secret, not have dealers find out, etc.
I think that 150,000 theoretical figure is for the 1983 MTB Hoard which was about 50,000 gold coins. Might have even been from something Roger or someone else posted in the RWB Saints Thread. I've never read anywhere that the Gillio WF Hoard was not 100% of what the oft-cited 19,900 coins amounts to. Gillio is still around, nobody has ever suggested (certainly he hasn't) that there were other coins.
OTOH, the records for the 1983 MTB Hoard got destroyed and there was never a final accurate accounting from MTB or Stack's, to my knowledge.
I think I just got my hoards confused.