Also a seller, this went into effect as early as 4:30am mst on Sunday. I know, because I was awake and saw it.

Amazon nerfed new FBA inbound shipments from sellers thru April 5. This new ~April 20th expected ship date is just about exactly the time it would take inbound shipments starting on April 5th, to distribute thru FCs and become active for sale.

Amazon is attempting to level the playing field for the sellers that got iced out during the inbound lockout.