If course you're right!
My first engine was in fact a Diesel.
The Cox .20 came later
Mind, that was over 50 years ago.....
Similar for me, a DC Merlin 0.75 cc in 1972 or 1973. Followed by a Cox PeeWee .020, and much later on a pair of TD .020s (and a TD .010). I still have two 0.55cc diesels now (r/c ones - throttled and silenced)
However I have only flown electric for the last 23 years.