I hear you on the cruise intervals. They do take concentration, particularly on the trainer.
The training effect isn’t significantly different, other than the fact that you are extending the time in zone 3 from 6mins to 10mins . If you find that doing your intervals in this progressive manner feels good to you then I would say try it out. On the trainer I also recommend doing a cadence change to break up the monotony, so every 3rd minute dropping cadence by 10 rpm then next 3 min block increasing cadence by 10 rpm – while maintaining steady power. Mimics terrain changes you find outside, and makes the intervals go by a little faster.