Its amazing what a difference doing really messy intervals does to HR. I did this recently on a fast group ride (well informal race really!). The power isn’t that high (just a bit over FTP) but my average HR was 96% of max! If I did 10m at that power at a steady pace I don’t think I would even get over threshold HR.
So what I gather from this thread is that this is really good VO2 max training even though the power is low?