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On their single pivot SLR brakesets, Shimano provided the option of two spring settings. The spring ends fits into the hole of a black Teflon (?) block anchored to the stop on the caliper arm. This block decreases the friction with the spring, decreasing lever effort, increasing modulation and allowing for a lighter spring. The hole in the block is also off-centre. The orientation with the hole closest to the stop is for SLR/spring assisted levers. Flipping the block 180 degrees, so that the hole is farther from the stop increases the spring tension, which will aid caliper release and pushing the cable back though the housing. With the introduction of dual pivot on Dura-Ace, Shimano introduced a cam style adjuster so the the spring tension can be altered more simply, by turning a flat bladed screwdriver.

You may be able to alleviate your problem with lever reset by switching the orientation of these blocks for the higher spring tension setting, though at some expense of the light feel and modulation of the SLR setting. If the blocks are set in the higher spring retention position on his calipers, it might also explain why the OP considers them to be satisfactory with the SR levers.

Traditional brake caliper performance can be improved by duplicating the friction reducing function of these blocks. A short piece of the Teflon liner from brake cable housing can simply be slipped over the spring end to reduce the friction between it and the anchor. This also eliminates the dirt build-up associated with the alternative of greasing or oiling the spring-anchor interface.

Just in case the OP gets the mistaken impression that all Campagnolo drilled levers are Super Record. it should be noted that Campagnolo also offered drilled levers on their Victory groupset. However, these are readily distinguishable from Super Record by their use of the Campagnolo shield logo with the winged wheel. Then of course, there all the aftermarket drillium variants.

Gran Sport brake levers looked similar to Record but didn't have the box outline around the brand name.

Among the Campagnolo variants are the only differences brake hood color, drilled holes, and logo? No functional or materials difference and made to equal quality?

OPs levers, I think, are gorgeous. If I had those I'd be tempted to build a bike around them.

My 7400 levers are non aero. It really depends on the year.

No, there were differences in curvature, thickness, taper and finish quality. There were also different bodies and clamp fittings, but I'm not sure when that came about. Some of the differences in the levers were very apparent when side-by-side. Whether those differences matter to you, that's your call.
To me, it does. Lots. Cheers, Eric