^^This pretty much sums it up.
Training like this makes sense if time or distance are limited. The amount of energy that it takes to move 185 lbs of rider and bike 40 miles is about the same amount required to move 250 lbs 30 miles. I suppose this would help if you have a short commute to work and maintain a certain pace with added weight.

As stated, OP did not indicate what this training was for. If general strength and endurance: sounds good. But different training strengthens different muscles. If this is for racing, it may be adding to unnecessary muscles that aren't used for the intended application.

My only critique is to agree that stacking weight on your back can lead to nothing good. Get some panniers and save the weight on your spine.