You're not quite right, no:

* An installed *public* version will only receive *public* updates.
* An installed *prelim* version will receive:
  * For *public* add-ons, *public* and *prelim* updates.
  * For *prelim* add-ons, only *prelim* updates, since serving *public* updates would prevent further updates until the listing is bumped to full review.
* And installed *beta* version will receive:
  * For *public* add-ons, only *beta* updates, since serving a *public* update would kick users out of the beta channel.
  * For add-ons with any other add-on status, no updates.

The aim of this PR is to prevent users of *public* versions from receiving *prelim* updates for add-ons with *prelim* status.