https://rideapart.com/articles/how-to-use-your-brakes
The point of squeezing rather than grabbing is to slowly apply the stopping force to the wheel. This causes weight transfer to the front wheel, so there's more force of the tire to the road, allowing you to apply more braking force all the way through to the ground for stopping. If you grab the brake, there's less pressure on the front tire, so it takes less braking force to cause the wheel to lock up. Proper squeezing should still be only a fraction of a second, but easing into the brake rather than just jabbing it will cause the suspension to assist with stopping force.
I'm not sure how sophisticated the ABS on entry-level bikes is. I'm used to older automotive ABS, where it basically just watched for the wheel to stop when it should still be moving, and released the brake for you (all of this happening multiple times a second). If it's a similar basic system, you'll still want to maintain good squeezing technique to load the suspension and produce optimal stopping results, but you don't need to worry nearly as much about accidentally applying too much force and locking the wheel. If nothing else, it'll keep you from screwing up when you switch to a non-ABS bike.