This is true, but we also have to acknowledge that consistency is _fueled_ by something. Sometimes intensity helps us get over a psychological bump so that we see some initial progress and then want to keep going. So it's good advice, but it won't be that helpful if it assumes 100% self-control. Self-control is the hard part.
'Tis better to consistently put in a moderate amount of effort over time, rather than putting in a lot of effort sporadically.