To my mind, they are both a form of sleep deprivation. I would say that sleeping poorly, no matter how long you lay there, still constitutes sleep deprivation.
And as people get older, they tend to both sleep less and also sleep less deeply.
Maybe it’s worse than that. If eg a long term lack of REM sleep lead to Alzheimer‘s (it seems to create dementia patterns at least), and people with disturbed sleep get virtually none of that, then they might be worse off than someone with just 5h of sleep.
Having had some very serious sleep issues in the past due to health issues, I would not disagree that sleep quality matters more than how many hours you sleep per se.
And as people get older, they tend to both sleep less and also sleep less deeply.