If someone begins intense cardio training and develops their heart muscle, it seems to me that the increase in volume of blood that the heart can pump with every beat might manifest as a higher systolic blood pressure. Is that right? If not, why not?
Intense cardio training over sufficiently prolonged time tend to incerease the capacity of your cadiovascular system to carry oxygen to the muscle. One aspect (among many) is the increase in volume of the left chamber of the heart which is seen in professional athletes of enurance sports. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4771151/) Blood pressure rises in excercise (not easy to measure, but can be observed in stress tests, https://www.ahajournals.org/doi/full/10.1161/hs0901.095395) to accomodate the need for extra oxygen. As the excerise continue, the arteries diameter get larger and it helps in regulating the blood pressure. It suppose to go back to normal as exercise stops and it actually goes lower than usual (https://www.ahajournals.org/doi/abs/10.1161/01.cir.83.5.1557 since the blood vessels remain large. You can also test it on yourself) for a few minutes after stopping. Prolonged aerobic training helps to reduce hypertension.