I agree with your first part of the statement about the top guys stressing their machines more than Joe Average but as to your last sentence, how many of the bikes in the field, other than the 690's, are not
enduro bikes? The WR, CRF-X, EXC, 570 'Berg, BMW-X, RX-V even the Husky are all enduro bikes modified for the Dakar.
The EXC might not be "the way to go", but it's a damn good compromise for the Joe Average. Rallye kit it and do the Yilgarn and then straight into the Aus Safari. Strip the Rallye gear off and take it to an enduro and smile all day - both days
. A 3 hr Pony Express in ironman? No problems. Bolt everything back on and enter Desert Challenge? No worries. Will it grenade? We'll see ... but 72 hours so far and still sounding sweeeeet
. Only oil/filter changes, valve clearance checks (never moved from new), and a DirtTricks cam chain tensioner is the only attention the engine's received.