A user Max's comment:
"The specialness of the temple check is that it's one of the few temple checks that actually works as advertised in the manual, i.e. increases by 1 for every 5 temples built. Pretender and prophet checks work this way too IIRC, but most other temples just check against your starting Dominion."
To repost Endoperez:
"Dom2 thread in which Kristoffer says something similar to Max's first comment:
http://forum.shrapnelgames.com//showthread.php?t=22651
Dom3 thread in which Twan's test seemed to support the above, even though Kristoffer said that the manual should be right.
http://forum.shrapnelgames.com//showthread.php?t=32396"
Kristoffer has since said that temples only spreading by start dom is WaD, so the only "bug" is that the dominion panel claims your temples spread better than they do.
In game terms, this means that a start dom of <3 is almost entirely unfeasible, because any opponent with 6+ dominion can easily out-temple spam you (and each temple will be more than twice as effective).
As a side note, Juggernauts are probably affected by temples, because it auto-spreads like a pretender or a prophet, so assumably uses the same mechanic.
If you want to dom push, you might not want a full 10-dom because then you need to "fill" all your home provinces to or close to 10 before they will really start to spread (meaning it takes longer for your dominion to start overriding your opponent's). 6-8 might be more effective