It's a bit variable depending which site you're on, some say they're not allowed to send them filled and you have to take it somewhere to get it filled; some say sealed and tested (generally a bit pricier, naturally); while others don't mention anything about it at all.
All in all, I figured buying the AGM was a safer bet, plus it's the one recommended on wemoto as an upgrade to the original, 11Ah v 7Ah and 140 CCA v 70 CCA.
Old style lead acid batteries are now sent 'dry charged' you have to get them filled by someone who's got a licence to handle high concentrates of acid.
Basically, they charge them and remove the acid, they can only be stored like this for maximum of 24mths, so check the battery date if older return it. They're then refilled, left for approx 30mins, test voltage 12.5v or above it's good to go, below 12.5 charge it.
Later