In reply to Penny Suarez.

I did not even think to check reusable blocks. I did a quick test and didn't see them listed in the inserter. I am guessing they are currently limiting what can be inserted into the sidebars/block-areas while this is in beta or for the "1.0" of this feature.

I'm not sure why Jetpack forms do not appear. I'll have to do some digging to see if third-party blocks are not shown at all or if it's specific to the plugin.