For online upgrades you now need at least 4GB + 4GB swap imho, because compiling assets whilst simultaneously running the site now requires much more memory.
If you are ok doing command line upgrades only, then 2GB (+ significant swap: 4GB?) might be ok … but I’ve not really tested that personally recently as I’ve moved all my sites to 4GB servers.
In any case you are right: that 1GB statement is really out of date.