Yes, that's correct.
This oil-water heat exchanger appeared for the first time in the 230 SL parts list B (10097) as of November 1964 as an option for the 230 SL - 3/4 of a year before the 250 SE came into production ...
I had a hard time retrofitting it. Everything went in nicely with the exception of the long (250 SE) oil tube. The front bend was too wide and interferred with the cold start fuel line of the R11 pump.
We (well we ..., my friend Hans-Werner did that) had to adapt the front bend of the oil line (by heat), then it was okay.
On Waqas early pics you can see that the 230 used a different oil line composed of two metal elbow pieces and a center metal-mesh covered rubber hose instead of the all-solid metal line that the 250 SE had. Since the earlier 230 parts are NLA we had to work out something.
I am well aware that the 230/250 oil/water heat exchanger by far isn't as effective as the oil/air heat exchanger of the 280 set up, but it increases both, the amount of engine oil and water. And both helps the thermal health of the sensitive 230 engines for sure.
Achim
(trash parts collector)