I can vouch for 2:1 with reduced volume but still with intensity from my recent training! And being so time crunched, on 4hrs a week of 50:50, 2hrs intervals and 2hrs steadyish. I’m 54 and going faster than I have in years!
Although I would like some more customisation based on age and the ability to customise plans further taking into account a number of variables, which I know will make it difficult for the Systm plans.
I agree wit the last post by @Coach.Andy.T about intensity and frequency having just been forced into this position due to “Life”! I’ve had a few weeks where overall frequency has dropped as well as total volume, but I’ve kept intensity with 3/4 half hour intervals per week and one steady ride so a total of only 4hrs. I’ve posted it here FWIW.