For Sale: Rembrandt Drawing, Signed by Basquiat

So, I recently signed up for Phil Schaap's jazz e-newsletter, which so far has turned out to be mostly lists of things he has for sale.  Before going further, I want to say that I'm a fan of Schaap's long-running Charlie Parker show.  He is an incredible living resource and important force in promoting and furthering appreciation of the music.  I noticed a strange thing about the items Schaap has for sale, though.  Many of them are ostensibly rare records signed by, but not featuring, Wynton Marsalis.  Now, what I said above about Schaap also applies to Marsalis.  I have nothing against him and have enjoyed his music - he's clearly an important figure.  But why would anyone want (to cite just one example of an actual item for sale) a 78 of Fats Waller playing "Carolina Shout" signed by Wynton?  Or (to cite another example) a 1927 Bix Beiderbecke 78 signed by Wynton?  At least in that case, it's one horn player signing another's record, which maybe sorta kinda makes some kind of sense - or not?  Does Marsalis' signature on somebody else's rare record make it more or less valuable to collectors?  If you were trying to sell a rare Mickey Mantle baseball card, would you get A-Rod to sign it?  I'm honestly confused.

Update:
Here's something I have no confusion or reservations about - hours and hours of archived Phil Schaap broadcasts, available for streaming.  Gold mine. Treasure trove. Cornucopia.