We already knew the release - but it's 'Shipping Now' folks!

So with a "street date" of April 13, can stores sell it as soon as it is in-hand, or do they have to wait until the 13th?

They have to wait. Most online sellers also will not ship it before the 13th.

Asmodee requires stores to wait until the street date.

A couple years ago, distributors would ship it immediately and then stores would sell it immediately. This led to some online retailers being able to ship a product and have it arrive before stores in some areas even had it to put on shelves. I know my local stores would have stuff 4-6 days before some stores across the US.

So to combat this, they started street dating everything. Now distributors don't ship it until it will arrive on Wednesday, and then it can be sold the next day. (At least my store gets FFG stuff in on Wednesday)