It's actually a bit of bad math. Stocks can be categories in a few ways, and the most common is their size and their valuation.
small cap and large cap
value and growth
Small and value companies are inherently more risky and less popular, so there is the idea that you can invest in them and get a premium i.e. more return. This is called alpha risk and there are a ton of articles and papers on this. There is no alpha for large cap and growth.
BUT
This shit goes in cycles. Over the long term value/small cap will out perform, but there will still be periods of time where growth temporarily out performs (usually right before a bubble crash). The issue is that the current cycle has been a massive bull run of large cap growth caps. So investors improperly think that investors should go for growth while they are younger and then swap over later. hence why it's popular to go for SCHG and SCHD.
There is a genuine argument to be made that these cycles are so large that you should be able to easily predict the crash. BUT right now valuations are still sky high. Going for a long term play on a growth index is a bad play.
If you compare SCHD and SCHG for their dividend growth, SCHD easily wins. Someone suggesting SCHG is arguing that you ride the growth cycle, hoping that it continues, and then sell later on.
I'd rather suggest you just stick with SCHD since it's 1) passively index 2) the best dividend growth fund that exists.
Pic related look at the two's dividend growth comparison