I typically do a small pour over sparge for a couple reasons. One being is that it removes the burden of doing water volume calculations. I typically mash in close to preboil volume, so my pour over volume is only what I lose to grain absorption. This allows one to measure and adjust the preboil volume during the process very simply by sparging to a volume rather than sparging a predetermined calculated volume. I simply have a few crude marks on my mash paddle for pre boil and post boil volumes, that's all that REALLY matters IMO.
and NOT pre calculating water volumes out to 0.001 gallons lol
The other reason I do a pour over sparge is to max out my kettle when making large batches that won't fit full volume, or won't conveniently fit full volume without being at the kettle rim, which is messy and inconvenient.
I also employ a technique where I mash in with limited strike water to save a bit of time vs heating full volume, after 20 -30 minutes of mashing, my sparge water is up to 170 and I will infuse an addition (IDK maybe 10 - 30% total water) of hot water to bump the mash temp slightly to compensate for losses, also a time saver avoiding the time to heat full volume to strike. This is typically with 15 gallon batches, so the time savings can be significant to get the mash started asap.
I prefer to do a small volume pour over sparge not as an efficiency improver, but rather just to simplify the process by sparging to a desired pre boil volume. I find it much easier to measure the actual volume in the kettle rather than attempt to pre calculate the volume to be obtained.
Yea I'm an engineer yet despise calculations and prefer to use a dip stick, go figure. Kind of like how an experienced carpenter will use a storyboard or template, while the engineer will calculate dimensions...what's easier???