no, that's incorrect.
maemo is a full good linux. period.
meego will be a full good linux. period.

easy debian allows to run a plain debian parallel which lives in a chroot and can't access files and directories outside that chroot.

screwing up your installation is possible in every kind of installation.

easy debian in its _current_ state does recommend _not_ to install additional apps or do upgrades. depending on the man power and effort available to the easy debian project, those limitations are likely to go away in a more or less near future.

having followed the market for the last few years, i say maemo/meego based devices are the closest you will come to a full linux on a smartphone.

conclusion: if you are looking for a smartphone with a linux almost identically to your desktop, maemo/meego is the only way to go.
if you are looking for such a smartphone in a near future (imo for the next 6 to 12 month) the n900 is the only device.

ps: there's a project called "moebian", attempting to re-debianize maemo (and possibly meego) to make its packages fit in with plain debian, thus making the n900 running plain debian and thus being able to use all debian packages w/o needing something like "easy debian".
i have no idea, how realistic that is and how far they got so far.