I've found an issue with the multi selection on extendedDatatable component. The problem appear if you try to select some rows to the next to last row with shift + click : the last row is automatically selected.
You can see this bug on your demo : if for exemple you want to select all rows between Virginia and Wisconsin. You click on the Virginia's row, and then shift+click on Wisconsin's row (the next to last row displayed). But unfortunatly, the last row is selected with (Wyoming).
Thanks for your attention.
unfortunatelly this issue really exist and seems you're the first who reported it before and after last 3.3.x release. https://jira.jboss.org/jira/browse/RF-8636 Currently we have no plans to continue with the branch.. so seems need to look for some workaround :/