A combined head-to-head record is usually presented as a single line of wins, draws and defeats. Splitting it by venue removes most of the apparent pattern and leaves the part that matters.
Home advantage dominates the record
Across football as a whole, home teams win considerably more often than away teams, and that effect is larger than nearly every club-specific matchup effect people look for.
A record showing one club well ahead frequently turns out to show two clubs each winning at home, which is simply the base rate in action.
Presenting the combined figure therefore attributes to the fixture something that belongs to the venue.
Unbalanced samples distort the total
League meetings alternate venues, but cup ties, playoffs and neutral-ground finals do not, so a long record often contains more matches at one ground than the other.
A club with an extra home fixture in the sample looks stronger in the head-to-head without having been stronger in any meaningful sense.
Checking the venue distribution before reading the record catches this immediately and is almost never done.
The interesting cases are the exceptions
Occasionally the split shows something genuinely unusual, such as a club with a poor overall record that has consistently taken points at the stronger side's ground.
That is worth investigating, because it suggests a tactical fit rather than a venue effect. A team set up to defend deep and counter may travel better than it hosts.
The mechanism is checkable. Look at whether the away performances shared a shape, and whether the current squad can still produce it.
Home advantage is not constant
Its size varies by league, by stadium and over time, and it has narrowed in recent years for reasons that are still debated.
Individual grounds differ too, with travel distance, pitch dimensions and crowd proximity all contributing at different magnitudes.
Applying a single average adjustment to every fixture is therefore approximate, though far better than applying none at all.
What to do with the split record
Read the away record against the away base rate rather than against the home record, since the two are answering different questions.
A visiting team that has drawn repeatedly at a difficult ground has outperformed expectation, even though the record shows no wins.
That reframing is where the small amount of usable information in a head-to-head actually sits, and it disappears entirely in the combined figure.