Unfortunately, we'll never know.Richmond weren't "so far ahead of ayone else that year," the Prelim v Cats showed that - though the Tigers held a comfortable margin. But had Collingwood by some chance won their home PF against a badly weakened interstate team there would have been a father of a hiding waiting for them 1 week later. The GF showed that. Collingwood beating a Richmond during a typical slow early season period in rd 2 does absolutely nothing to change that. Richmond won its final 12 matches in 2019 with some obscene % & conceded just 20 goals in 3 finals(Richmond kicked 47.) Collinwood - who scored 3 goas to 3/4 time in the PF were never getting near that. You are dreaming.
Collingwood would have been considered more likely to beat Richmond in the 2019 Grand Final, than we were in the 2018 Preliminary Final, and we all know what happened there.
There wasn't a massive margin between Richmond and Geelong in the Preliminary Final, and Collingwood had already beaten Geelong in the finals series.
Richmond, GWS. Collingwood Geelong and Brisbane were all contenders that year