The most unfortunate part is that people keep posting this nonsense even though the its been shown to be wrong over and over again.
For the umpteenth time,
Samsung (probably in order to cut down on complaints) has designed the mutliwindow functionality such that an app has to explicitly say it works in the Mutliwindow environment, rather then just allowing every app to show up there. Most apps seem to work fine, but some don't because the screen is designed for a specific range of aspect ratios, or because the app has designed to pause when it didn't have focus. Many people have added support to a lot of different apps without any intervention for Verizon.
This means that at the very least, an app has to be recompiled with the needed flags set before it will show up in multiwindow. It appears that in their rush to get out Mutliwindow support with their initial launch, Verizon did not recompile all of the apps that some other carriers did when they added support for Multiwindow later. Verizon didn't do anything to block those apps, they just didn't provide versions that worked with MultiView. Given the apps that they did provide, it seems likely that the rest will show up in a coming update.
I'm looking forward to that update. Partially to get the additional apps, but mostly so that people will stop spreading the FUD that Verizon has done something to block apps.