Haven't seen the article, so I'm unaware of the "why". Shooting from the hip, here's my take: We have a ’99, and it’s the best 4.0L engine, PCM, overall package. Later have coil-on-plug ignition and a less desirable cylinder head, earlier '96 and '97 have transition from OBD to OBD II electronics. ’91-’94 would be acceptable, some 4.0L sixes in this era have piston noise issues (typically when cold) from block core shift, not necessarily a reliability issue, more a nuisance…’87-’90 is the Renix EFI/MPI, older technology and a less efficient cylinder head, not terrible, just a totally different troubleshooting and diagnostics approach that makes the '91-up Chrysler MPI/EFI system attractive. Of course, for home diagnostics, OBD II is superior and more accessible to an inexpensive code reader or scan tool.
’96 takes the hit for transition from OBD to OBD II issues in the electrical and electronic circuits, some carry to '97. If you notice, there is no "1996" YJ Wrangler, and the first TJ (1997) bursts on the scene with OBD II circuits incorporated. XJ Cherokee sales projections for 1996 were too strong to skip a model year, so haphazard OBD II wiring, electronics and an OBD II type PCM strategy went into place on this model.
Though they do not list '84-'86 XJ Cherokee models (as most won't), these vehicles are okay with the 2.5L four (if you like four-cylinder power), better yet the 1986-90 2.5L four with TBI. If stuck with a 2.8L V-6, consider a G.M. 3.4L bolt-in V-6 crate motor replacement that eliminates the weak small journal crankshaft, rear main seal leaks and other quirks with the early design 2.8L V-6.
As an historical point of interest, AMC got stuck with this early version 2.8L V-6 engine through 1986, even though G.M. vehicles went to a better/bigger journal crankshaft and rear main design in the 1985 2.8L V-6. If the 3.4L V-6 crate engine is still in the G.M. parts inventory, listed as a direct replacement for the 2.8L V-6, you can get respectable performance and have a carbureted V-6 that actually works. I would expect to pay a song for any '84-'87 XJ Cherokee, the only incentive for buying one.
I’d say the Jp assessment is reasonable. There are quirks with any of the XJ Cherokee model year groups, and items like the vacuum disconnect front axle come to mind for earlier years—the ’98-’99 might have the least foibles. Overall, the XJ Cherokee offers an inexpensive price of admission and often matches the Toyota 300K Mile Club for reliability and longevity. I might add that it's much easier to service and restore an XJ Cherokee than any Toyota truck in that year range!