You need not worry about the locks seizing (Among other quality control issues) if you're buying a lock from a reputable source and from an acceptable price point.
The only locks you should be hesitant of, are the unnamed, unknown, cheap ones. that have no one to back their standards.
The one you posted there is fine, it's cheap but not cheap enough to be of concern and onguard are reputable.
Though, that clocks in at 930 grams. I do think it's pretty heavy compared to the prior options.
As of your cleaning concerns, WD40 is acceptable, it's a solvent so it eats and dissolves Rust and Grime that'd otherwise cause your lock to seize, actual lubricants (such as Lithium grease sprays) Will Attract dirt and worsen the problem as metal-on-metal wear & grime occurs. -- it'd be attracted by the lubricant, not the solvent.
IMO Locks don't need lubricating, they just need degreasing, WD40 is more than acceptable for that.
Anyway, as you're trying to keep your lock criteria small, lightweight and secondary, I still maintain You're going to have trouble finding those criteria with D locks, as almost 99% of the time D-Locks are Primary locks, so they're big & heavy.