Sparging is just rinsing to get all the sugar into the wort. I always thought the BIAB method was just to keep everything in a single pot and you still needed to sparge to get your gravity and volume right. I guess I learned something.
I've done it both ways, as I've said.
@cryano here's what to do next time to get your volume right on, if you want.
Grab a 5g bucket. Heat up a gallon or so of water to 170F. Put your grain bag in the bucket after its finished dripping into your main kettle. Then pour the hot water into the bucket over the grain. Stir the grain around in the water a bit, and let it sit 10 mins.
Then remove grain and add this wort to your main kettle to get your pre-boil volume you want.