Yes, I think the term redundant indicates that the central tendon has popped which makes this a high grade injury with a longer recovery time.
I have experienced what you describe many times and it is not unusual for me to scan a hamstring and be happy there is a subtle but significant tear and then for the radiologist who is viewing it in real time with me to be unconvinced that it is a certain abnormality. They can be very subtle sometimes on ultrasound. In this case I always suggest a quick MRI sequence through the area to prove me right or wrong. The radiologist is always happy with this as they will then have confidence in their report. When you do the MRI the injury is MUCH worse than I expected. So the MRI will always show the complete extent of the injury as it is so sensitive to the oedema and extravasated blood products. The ultrasound certainly underestimates the extent of the injury in my opinion.
DOMS and rhabdomyolysis are a bit different to a tear. Firstly and most importantly the history is different. With a tear there is a clear history of an acute event which stopped the person performing the activity or at least an acute awareness that something had gone wrong. With DOMS and rhabdo the pain comes a day after the activity and there is no clear point of acute injury.
Secondly a tear affects a defined area of the muscle architecture , for example the proximal MTJ etc but DOMS / rhabdo tend to affect the muscle more globally.
You could have a patient who was tracking to an inevitable DOMS / rhabdo event and then did an acute tear as well. This would be tricky, but I still think you could make the diagnosis based on the history and imaging findings.
Steve