You are right as usual. It is 8mm.
The fiche says 92002-1713 BOLT, SOCKET, 10X17
Is the 10 for 10mm diameter? Shouldn't it say 8x17 ?
Convention is confusing here. Is JIS different?
10x17 means that the bolt shaft is 10mm diameter and 17mm long.
It make no reference to the means of tightening/loosening the bolt other than "SOCKET" which indicated that it needs an Allen Key.
If it had said M10x17 then that would imply 10mm diameter shaft
with a 1.5mm thread pitch.
As it is it doesn't specify the thread pitch at all.
Japanese Industry Standard (JIS) is their equivalent to ISO or ANSI.
On our motorcycles and cars the only time we come across JIS stuff is with their "equivalent" to the Philips screwhead.
To be honest JIS screwheads are just 100% better than Philips and should be adopted as the ISO world standard, but then getting people to agree on such a change would be harder than negotiating a lasting peace in the Middle East.