Looks like this is broken from beta-20 onwards (email@example.com) it works fine and as expected with previous versions.
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RE: [ v1] Dialog plugin - persistent property does not work. (firstname.lastname@example.org)
[ v1] Dialog plugin - persistent property does not work. (email@example.com)
code pen: https://codepen.io/anon/pen/zXgjVo
Even below properties are not taking into effect: