That's not what they did in either case. The Mini 3 was literally just the Mini 2 with TouchID, and they sold it at the same premium price as when the Mini 2 was new (and on par with the full sized model). The Mini 4 was an upgrade and slight re-design putting it almost on par with the then flagship Air 2, again sold at premium price. Neither of these models represents the strategy that was suggested above.
It's exactly the same strategy, just presented in a different way. I'm surprised you don't see it.
The introduction of the iPad mini 3 in October 2014 resulted in the iPad mini 2 being dropped to $299. This is the n-1 strategy. Take the current tech, back up a generation, and lower the price. The latest tech in 2014 was Touch ID and A8. The iPad mini 2 used A7 and lacked Touch ID.
In 2017, the latest tech is A10 and laminated display. Apple applied n-1. The iPad (2017) uses A9 and non-laminated display. Price is $329.
When Apple launched the iPad mini 4 in September 2015, the iPad mini 2 dropped to $269.
Apple has tried the n-1 strategy on the mini. Then they tried n-2. It failed twice. The iPad mini sales volume continued to drop and including the mini's proportion of iPad sales.