As a side note I think where some confusion may be coming from is that Hankook used to do an AGM battery of similar size/capacity with the same model number (M31-950):
www.tayna.co.uk
I can see what looks like physically the same batteries with the same model number/capacity/CCA at some very fringe sites which very little info - but often described as "maintenance free" which is generally only used in advertising with flooded batteries.

AX31-950 Hankook Deep Cycle Leisure Battery 12V 100AH
M31-950 Hankook AGM Leisure Battery Hankook are a pioneer in the battery industry and have been for the past 75 years. Challenging the quality and quantitative growth of the battery industry. Based in Korea, Hankook has a global network that has been strengthening its distribution...

I can see what looks like physically the same batteries with the same model number/capacity/CCA at some very fringe sites which very little info - but often described as "maintenance free" which is generally only used in advertising with flooded batteries.
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