Excellent points, above. ^
It also depends on where the recipe comes from. Most commercial kit recipes and recipes in brew books, AHA, etc. are typically based on 5 gallons in the fermenter, trub and all. All grain recipes of such are or should be standardized at 75% mash efficiency, but beware of unmarked outliers, I've seen many of them.
Most, if not all recipes posted in forums, on websites (e.g., Brewer's Friend, BeerSmith), blogs, etc., are typically what the homebrewer brewed on his/her system. So mash efficiency (thus amount of grain used), trub volume left behind in kettle (left out of fermenter) can vary largely.
I'd say best is to run recipes through a recipe formulator (BeerSmith, Brewer's Friend, etc.) using your equipment and process variables.
Try to keep the ingredients proportional (percentages of ingredients the same or close).
Hops themselves vary, their oil content and Alpha Acid percentage as well as aging effects due to extended storage in non-frozen state.
So use the %AA of your hops, not theirs, and try to match IBUs.
That will get you in the ballpark, but there will be process variables that will make your brew unique from the brewer who posted it.