Any exercise in which even a minor pause is taken between repetition is Cluster Set Training.
Sure, but it's one giant cluster with no extended breaks making it a cluster set of let's say 1x1/50 instead of 10x 1/5 and fatigue sets in after the first half dozen and then everything after that suffers. Even clusters need inter set rest in addition to the intra set rest.
It's unlikely the isn't Custer Set Training. I thought about elaborating more in my reply but opted for a shorter response, which I now regret.
Cluster Sets
The rest periods between Cluster Set is between 10 to 45 seconds, one minute maximum.
By definition Cluster Sets are composed of short Intra Rest Period between a repetition or set of repetition, with Inter Rest Period Sets; rest periods between Set of Cluster Set.
Muscle ATP Restoration
As you know, Cluster Sets allow Muscle ATP Restoration. Research indicates that up to 50% is restored in approximately 30%. Dr Greg Haff found that just under 80% was restored in approximately 45 seconds.
It is unlikely that someone practicing the Pole Vault, High Jump, Long Jump, etc watching the clock and performing them with rest periods that short for 1 X (50/1): 1 Cluster Set X 50 Clusters X 1 Repetition Each.
The reality is the they are performing...
Traditional Sets
Most are taking rest periods between Vaults and Jumps al are longer than one minute. Taking longer rest period allows for more complete recovery.
Research shows that approximately 3 minute or longer is required for Muscle ATP Restoration. That means, longer rest periods ensure greater force production.
Inadvertent Cluster Set Training
Ironically, the majority of individuals who resistance training unknowingly are performing Cluster Sets with Limit Strength and Hypertrophy Training.
At some point in a repetition set, when they run out of gas, they take short pauses between repetitions Doing so, means they have turned a Traditional Exercise Set into a Cluster Set.
It slightly evokes a different training response; modifying the intended objective and outcome.
Muscle Fatigue And Technique
Yes, as you noted, once muscle fatigue sets in good technique/skill is altered, promoting poor technique.
What it does in make a lifter more comfortable at performing the movement wrong.
It take time and persistent practice in performing the movement correctly to develop technique and most importantly to maintain it.
Assembling Something Incorrectly Analogy
Once poor technique is developed it takes even more time to de-program and re-program good technique. I have personally experienced it myself and in working with other.
It amount to putting something together incorrectly. It requires additional time and patients to take it apart and then assemble it correctly. As the saying goes...
"
If You Don't Have Time to Do It Right,
When Will
You Have Time to Do It Over?"
With that in mind, let me hammer this point home again.
1) Performing the Competition Powerlifts as Training Exercises develops Limit Strength at the expense of Technique.
2) The key to increasing Limit Strength in the Competition Powerlifts is accomplished with Auxiliary Exercises that are similar in nature to the Competition Powerlifts.
Auxiliary Exercise are somewhat "Disposable", in reality they are "Recyclable".
They should be pushed to the failure or near failure in a Training Cycle. Then that particular Auxiliary Exercise is discarded and replaced with another Auxiliary Exercise that is similar the Competition Powerlift.