Nope, that mess with pDHS I mentioned above? Caused by a real life mess up and a line in TRO: 3050 or somewhere else giving the Capallens DHS mounting Cataphract's or something in 4SW, so whatever design that is is the first 'mass production' design to mount pDHS
no it was the BJ-3 that caused the issues.
the
battlepack: Fourth Succession War introduced the BJ-3 Blackjack, with full DHS. and also used it in a scenario set in 3030 (Morgan H-D's raid of Sian, specifically) the BJ-3 in the battlepack was fluffed as being the very first mech with the rediscovered double heat sinks technology. according to Sarna the BJ-3 had been included in the slightly older
4th Succession Wars Scenarios Volume One, though since i don't have that one i can't vouch for that, but i know it appeared in the battlepack.
so many years later after Catalyst took over, TPTB later decided to change the introdate for the BJ-3 to 3042, as part of their reworking of the introdates for recovered technologies like DHS. this however left the established use of the BJ-3 at the tail end of the 4th succession war hanging, so they wrote up the BJ-3
X as an earlier version of the BJ-3 that made use of the prototype-DHS rules they'd introduced in
XTRO succession wars Vol 1 (and which they reprinted in
Historical: War of 3039). the BJ-3X got its official mention in
TRO: 3039 and then was again mentioned in
TRO Succession wars.
which slightly retconned the story in the
McCarron's Armored Cavalry (scenario pack) that you describes above. (
thank's btw, i hadn't known that detail! had to hunt to find the sarna page to get the source though) about how the Capcon's supply came from illicit deals with Kincaid Defiance Industries on Hesperus II, replacing the standard DHS with protoDHS.
though in my digging around Sarna, i also found mention of the short story
Proprietary that was published on Battlecorps, which was about that raid and the deal.