This seems like when they release GTAV one at a time on every platform to get people to buy it twice. I'm guessing they will release this remaster on all platforms, PC next, then they will release a full remake in the RDR2 engine to try and double dip everyone. They already recreated the majority of the original map for the epilogue of RDR2, so a lot of the work was already done. Plus they could resell RDR2 as a "next-gen" version to charge more than $70 for them together.
As far as business models go this one is easier to avoid falling into than games being designed around microtransactions. You just have to wait and get a better product eventually for cheaper. While mtx games are generally more expensive to get into the longer they run.