first i tell i don't represent debian here but i think i can answer some issues.
to make pepper flash update automatic is basically against debian policies. if i know correctly, adobe won't separate security related updates and feature updates, therefore debian cannot make flash updates automatic. it was new information to me that --unstable and --beta in update-pepperflashplugin-nonfree script. (even though i started to inspect script as well, slightly different reasons) however in this context stable, beta and unstable is google terminologies. google chrome has stable, beta and unstable, each has pepperflash in it. and it is up to google to update chrome package with newest pepperflash. basically put, debian has little control if google chrome has outdated flash in chrome stable package. flash is big security bomb these days, may i suggest to uninstall flash.
