Hey there Kelli,
I’m going to answer the question directly as asked, rather than place judgement on any stretching as you’ve already got that info above 🙂
How long should you stretch? It depends on many things: age, joint ROM and history, workout content through that day and the week, personal goals, etc.
Rather than time, I’d focus on quality dynamic stretching and SMFR before exercise based on what’s being worked. Generally 5 minutes is enough, some people like to spend more time. Very individual.
I’d say be present to what feels really good and helps with your workouts, and what doesn’t.
After workouts a couple static stretches for some people is important to help hamstrings, spine, etc. However, others who are VERY flexible and have ROM exercises within the workout, I wouldn’t even bother. Those individuals are already flexible and usually need more stability and strength work.