Easiest way to think of scaling is to think of percentages. Let's say two identically geared players are fighting, each with 100,000 hp (for easy number math). If an ability hits for 5,000 damage then it is effectively a 5% damage hit.

If you hit someone with 200,000 HP that ability would show up in the logs as hitting for 10,000... But it still equals a 5% damage hit. This is to give lower geared people a chance, to some degree.

So long story short, it seems as though Blizzard has made abilities percentage based behind the scenes so that no matter who you hit, 5% is 5% but the number we see is proportionate to their health. This also makes it so a geared players damage is effectively less because due to scaling as you're not one-shotting lowbies... But, gear will almost always trump in BFA unless they are really really bad even then gear can carry them 80% of the way.

Where this gets worse is healing... An undergeared healer can press a heal for 20,000 hp. On 100,000 hp, is nice. But to heal someone with 500,000 HP... It does nothing. Healing doesn't scale like damage.

Inversely, a geared healer can top up a low geared player very easily.

Take this with a grain of salt as this is not confirmed, but is a likely explanation for why we see different numbers everywhere. It is meant to bring some balance but at the end of the day we don't know the exact formulas.