Neil,
You need to consider that many of the ECR records are in fact duplicating each other, in some instances the one event was recorded in four different sets of records. In other instances NO record was made at all. And each time a record was made there's spelling errors as a minimum to be considered.
The NSW baptism of one of my grandmothers (several "g"s removed ! and pre 1800) is indexed FOUR times, and yet her younger sibling's baptism is not indexed at all. !
Very hit and miss, but when there is an ECR record, the Official Transcript is the better option in my view, UNLESS of course the OP can get to the NSW State Library and look at their copy of the image. HOWEVER, the NSW SL does not permit you to take a photo/copy of the image......
Cheers, JM