I think the refresh strategy for the Neo will be to eat up left over Pro A-series chips from the previous year's pro iPhone production runs. Since these chips are left over, they can go into one of a few devices, Apple TV, iPad mini, both of which are niche and low volume products, and probably don't justify annual spec bumps, so with the Neo, it was a good opportunity to vacuum up all the remaining A18 Pro chips.
I suppose the A19 Pro chips may need to be held back for use in the Studio Display XDR, the next iPad mini, and the next Apple TV, all of which may need to support a multi-year release cycle, and if the iPhone Air continues with no updates, that one too. In that case, then the Neo could possibly wait for the A20 Pro.
I suppose Apple needed another product that they could confidently use to vacuum up all the leftover binned chips, so the Neo was a very cost effective solution for them.