Yeah, wadcutter loads do seem to be a good bit dirtier than many other .38 Special loads IME too.
Yes, the overall length of the wadcutter rounds is necessarily shorter, so there's a longer "freebore" length to get dirty. (I presume BTW that you're meaning the insides of the cylinder holes, not just the front cylinder face.)
My own experience (I have two .38 Special LCRs) is that they clean up pretty easily, including the entire length of the cylinder holes, and all I shoot in mine is standard 148gr wadcutters, since those shoot right to POA in my hands.
(The few other .38 Special loads I've tried so far in these two LCRs, including Remington 158gr+P LSWCHP, Speer 135gr+P "short barrel" JHP and more recently Buffalo Bore 150gr wadcutters, unfortunately do not have as good a correspondence between POA and POI at 5-11 yards as I'd like, unlike in multiple S&W J-frames.)
Anyway, I patch out the cylinder holes and bore with M Pro-7 on a ribbed (not slotted) brass jag, followed by brushing them with a brass brush (.357 for bore, oversized for cylinder holes), followed by letting the cylinder holes and bore sit for about a half hour filled with Gunslick Bore Cleaning foam, followed by a few more M Pro-7 soaked patches.
(I brush the cylinder faces, recoil shield, inner topstrap and other frame areas with M Pro-7 using a nylon toothbrush. The forcing cone area usually needs more attention than elsewhere, of course.)
Anyway, I've had no buildup of residue inside the cylinder holes using this regimen, but I do clean the guns after every shooting.
Since your target implies excellent correspondence between POA & POI with 148gr wadcutters (not to mention a good hold on your part), I'd say that makes good sense.