Coexisting and Space Cannon Defense

I think I found an error in this site: https://twilight-imperium.fandom.com/wiki/Coexist specifically the text under the Coexisting and Invasions section:

However, both the controlling player and the coexisting player may have units with the SPACE CANNON ability so either player may use them.

Rule 77.6 states:

Space Cannon Defense
During the invasion step of a tactical action, after ground forces have been committed to land on planets, players other than the active player can resolve the Space Cannon ability of their units...

The rule states that "players other than the active player", which contradicts the website's statement that "either player may use them" (their Space Cannon).

My first question: is this actually an error on the website's part or I am missing something?

For my second question I have to give some context:

The step that confuses me is the subset 2 of Invasion:

49.2. Step 2 – Commit Ground Forces: If the active player has ground forces in the space area of the active system, that player may commit any number of those ground forces to land on any of the planets in that system.

Note that the rule states "If the active players has ground forces in the space area of the active system [...] (they) may commit..."

However, when reading the rules for Coexist in the Thunder's Edge rulebook, the conditional for having ground forces in the space are of the system seems to not apply (but I'm unsure):

Likewise, a coexisting player may choose to end their coexistence by activating the coexisting unit’s system and committing the coexisting units against the planet they are coexisting on

But the coexisting units weren't in the space area, they were in the planet already, however they seem to be committed either way, not from space but it seems that it also counts as committing those units. But maybe I'm wrong (that's why I'm here asking).

So my second question is:

Let player A have a PDS unit on planet X and no other units on that planet. Let player B play an action card or ability that allows them (player B) to place a Ground Force into coexistence on planet X.

• Player B activates Planet X's system without moving any units into the system. Can player A use its PDS' Space Cannon Defense ability to target the Ground Force that is coexisting?

Thanks