As you can tell, there is no "hard and fast rule" about how we count "cars". A friend and I were both in HO at the time and the standing rule on his layout was "a STANDARD when building a train is one locomotive to five cars plus caboose." Caboose were counted as "free tonnage" meaning, they were allowed for in the tractive effort required to "get up the hill".
Thus the trains on his layout typically limited to three locomotives plus 15 rolling stock and a single caboose. WHY? Because that train would fit most staging and pass tracks on his layout. And we knew which runaround tracks had a shorter clearance point.
It was not unusual to see a 3 locomotive set pulling 8 or 9 cars and a caboose simply because the train "had work to do" meaning set outs and pick ups and thus what left the yard or staging might not last more than the first industry on the mainline where there was a set out.
But if picking up a car from an industry put you over the 3 locomotives, 15 cars and caboose limit, you left the lowest priority car "in town, not spotted" so it was an easy pick up for the next train going in the direction that one car needed to go.
Yes, we would spot the car for easy pick up because we were leaving work for the next crew...and in real life, Bubba might not appreciate missing his kid's game because he got caught with a couple of pick ups you left him which caused him to sit in the hole until the southbound cleared that station or industry.
But if the next 3 trains had maximum tonnage before then got to that station and that track, it might sit for a couple of sessions (assumed to be a work day).