Yes, it's one for one as long as the training pipeline is already filled. When age 65 went into law, the training pipeline was shut down at UAL and most other carriers. Shutting down the training pipeline eliminates the need for pilot jobs which is why there were more furloughs when 65 went into effect than there would have been retirements.

I'd say that triggering 12 training events per retiree is way too high; I'd suspect the number is closer to 4 but I'm making a guess.
How many PIs are required to train those 4 training slots?
How many months are those 4 pilots in the training pipeline go without a line?
How many dedicated LCAs does it take to train those 4 pilots?

Add up all of those numbers and 25 retirements/month triggers a significant need for additional pilots beyond the 25 retirements/month. This is a one time need because once the training pipeline is filled, the number will remain static to train the replacements for 25 retirees/month ... this assumes no growth and no shrinkage. Obviously growth/shrinkage will effect the size of the training pipeline.

Much ado is made about UAL parking all of the guppies and some 747s. Those pilot losses could have been absorbed by retirements and very few furloughs would have resulted. The rule of thumb that I've heard is that it doesn't make financial sense to furlough a pilot for less than 2 years. Look at UAL currently. The 75/767 fleet is fat on pilots because of the parking of aircraft, yet there are no furloughs. Why no furloughs? Because age 65 retirements start in less than a year.