True, but also remember that often the Omron and other PID controllers are multi output types, and have a menu selection for output type, that is set for the particular variant you have. Thus if the one you get is relay only, and you want SSR output, you just have to open the case, and remove the relay, and put the 2 screen printed wire links onto the board, to convert the 2 connections for the relay into the SSR drive, so it now will provide 24VDC at 20-30mA to drive the SSR directly.
You can also install the optional second output relay, and get the alarm output, which can be used to turn off on sensor failure, or to switch a duel heater one into a high power mode for rapid warm up, putting both in parallel for rapid heating, then on approaching a temperature well under the set point it switches them to series operation, so that they then only put in slow controlled heat, or runs a phase angle controller to select a low part of the mains cycle to provide heating. Some also have a set of jumpers you install, to get a voltage proportional to difference, for driving a variable power input to the heater, so you drop power as you approach set point, and then the offset power stabilises at something just compensating for the losses.
There is a lot of smarts in the supposedly simple PID controller that comes in a DIN cutout, often with hidden network ability as well, just need to use a cable to link them to a computer or PLC.