That's almost always true. There are a few E90s that have 4 rows of 4 in J. There is a bit more legroom, but they are narrow. Certainly not worthy of a dime of my hard earned money.

Fortunately, those are very rare, but I've been upgraded twice to receive that surprise. The seating charts don't warn of this odd configuration in advance. They do, however, serve the J meal on these flights.

The other thing is that while CM doesn't offer a lie flat J seat on any of their aircraft, they operate a few 737-800s with some really comfortable reclining seats with footrests and lots of leg room. It's hard to find a more comfortable seat to/from Latin America. It seems that they prefer this configuration for LAX-PTY, and I've had them with less regularity to/from other destinations.