Yes, but we can all agree slim was a terrible choice. No reason for it to exist with pro being so close to releasing.
You're looking at this from the wrong perspective.
The Slim is not a new product, it's the way Sony could cut the PS4 price to 299$ (and even lower with future deals).
If it wasn't for the Slim the PS4 would still cost 349$ today or Sony would need to slash their profits.
So the Slim was not a choice or a mistake, it was a necessity.
Also about MS vs Sony it's clear that they're having different strategies with different timings that will bring fruits in different moments.
PS4 sales right now are obviously not at full potential because there is a group of consumers waiting for the Pro, those sales are not lost though, they are just delayed, in the meantime Microsoft had fire sales to 250$, deals with free games included, other specific deals at particular retailers, new hardware introducing extra features that are worth the upgrade for a group of existing owners. You really can't say that they aren't trying hard.
And with all this in the end what did they gain? Less than 200k over three months in their main market? That is nothing looking at the full picture, it's just enough to get a few PR headlines.
November+December are where the biggest chunk of the yearly sales are made, when Microsoft in 2014 was able to cut the PS4 lead in half in the US from 1m to 500k, it's not like the number of months that Sony won previously mattered much. That was a big success story for MS, so big that probably saved them, not 175k over the three summer months.
About Pro vs Slim sales, Slim is definetly going to sell more because it will get really attractive bundles and a price cut to 250$ on BF (and possibly beyond like last year). That won't happen with the Pro that will stay at 399$ and after the initial huge sales to core gamers and upgraders will be left as the more expensive option targeting a much smaller market made of core gamers and enthusiasts with 4K TVs.