I believe you are referring to mixing strength and hypertrophy in the same set-rep scheme. There have been a number of small research studies published in the past decade testing this concept. Small studies, but with results significant enough to get attention.
This is where all but the last set are strength sets (e.g. High Intensity and Low Volume) and the Last Set is a Hypertrophy Set (e.g. Low Intensity High Volume).
As long as your workout objective is not strictly strength, then there is no harm in trying this workout methodology. If you choose to give it a whirl, be sure to not violate the other guidelines of a workout that are generally agreed upon.
I would like to attempt to clear something for you.
Every workout consists of a combination of intensity and volume. This is at the root of the most agreed upon schema in weightlifting and strength training. At the same time it is one of the miscomprehended and misused.
Variations of Intensity and Volume is the heart of Classical Periodization.
International Weightlifting Federation's definition of intensity:
Intensity of load is the average weight of the resistance.
From page 393 of National Strength and Conditioning Association's, recommend resource to prepare for their CSCS exam, "Essentials of Strength Training and Conditioning" 3rd Edition.
Various repetition and set schemes affect the true intensity value
for resistance exercise and indicate the quality of work performed.
Instead of using time to calculate mechanical or metabolic power or
intensity, it is more practical to use a value that is proportional to
time to time namely, rep-volume. The more repetitions performed, the
longer the training session. Dividing load volume by rep-volume
results in the average weight lifted per repetition per workout
session. This is a good approximation for mechanical and metabolic
power output which are true intensity or quality of work
The above definition was written by John Garhammer, PhD., CSCS.
From American College of Sports Medicine's "Progression Models in Resistance Training for Healthy Adults"
Training volume is a summation of the total number of repetitions
performed during a training session multiplied by the resistance used
and is reflective of the duration of which muscles are being stressed.
Classical periodization.The classic (linear) model of periodization is
characterized by high initial training volume and low intensity, and
as training progresses, volume decreases and intensity gradually
It has been shown that systematic variation of volume and intensity
is most effective for long-term progression. Variation may take place
in many forms and manifests by manipulation of any one or a
combination of the acute program variables. However, the two most
commonly studied variables have been volume and intensity.
Volume is Sum of reps times weight lifted.
Intensity is Average of reps and weight lifted.
Examples of Intensity and Volume Set Rep Schemes:
High Intensity and High Volume
2 sets 12-14 reps novice
3 sets 8-12 reps intermediate
4 sets 8-10 reps advanced
High Intensity and Low Volume
3 sets 2-3 reps novice
4 sets 1-3 reps intermediate
5 sets 1-3 reps advanced
Low Intensity and High Volume
2 sets 12-16 reps novice
3 sets 12-16 reps intermediate
3 sets 12-16 reps advanced
Low Intensity and Low Volume
3 sets 4-5 reps novice
4 sets 4-5 reps intermediate
5 sets 3-5 reps advanced