Warmups are technically part of the work load true but they should be done in such a fashion that minimizes your fatigue and maximizes your performance and CNS stimulation.
For example, your first working set of pulls to the knee was a 1x3 @ 275. As a warmup I would do something like
Bar x 5-10 (just to get the bar in your hands and your body moving)
135 for 1-2 sets of 5-10
185x3
225x1
Then hop into 1x3 @ 275 and the rest of the work sets. Doing this will not add too much fatigue but get your ready to lift. It will also add in 10-20+ reps with submaximal weights to ensure your form is good and ingrain the right movement pattern. At heavier weights it will take less conscious effort to maintain your form. Obviously tinker around wih the warmup and find what works best for you. Some do better with larger jumps and less warmup volume bc they get taxed easily and some need more warmup work to get themselves ready to attack the bar.