I agree with what you've surmised wholeheartedly. My experience with Ruger Mark pistols goes back to 1969, so I know full well what they won't do to modify any already sold pistols, especially a Ruger Mark III design, which they now consider to be an obsolete version. They no longer even stock some of the parts for those versions.
It did quite surprise me that Ruger will now take in earlier Ruger Mark I and II pistols for drilling & tapping for an optics base. Even though they farm that work out to a local 'smith. I do recall a member on some forum who sent his Ruger KMK10 in to get it drilled and tapped. Whoever did the work drilled through and right into the chamber. That made the guy quite livid and their only response involved him picking out whatever Ruger Mark III version he chose for a replacement. I suggested that they ( Ruger ) should send the complete pistol to Clark Custom or Volquartsen for the installation of a new 10" barrel. Obviously, that didn't happen.
Another issue involves some of the Ruger Mark II stainless steel pistols that have two-piece bolts. Their customer service manager admits that they get between 3 to 5 Mark II, two-piece bolts back every year for replacement. Trouble is, they have no Mark II bolts left in inventory, so they were sending a Ruger Mark III bolt with smaller diameter bolt ears as replacements. Now that they're out of Ruger Mark III bolts, most likely they'll send Mark IV bolts if anymore bolts separate.
I done a preventive fix on well over 40 of the Mark II bolts and so far, none of those have separated, but don't ever send a two-piece bolt back to Ruger, EVER. They will automatically replace it, so I recommend that if an owner ever needs to send a Ruger Mark II stainless steel pistol back to Ruger, for any reason, don't send the bolt.
I have seen the two-piece bolt on stainless steel KMK 10, KMK 512 and the KMK 6 7/8 Heavy Taper Target pistols, and those also are found with the solid, one-piece mainspring housing assembly body.