knowing what I can maintain for 5/10/20 mins
That’s your power profile, not your FTP.
I’d say the article is more a warning about both blindly following a generic plan with interval targets based on percentages of FTP, and also about falling into the typical Jan/Feb turbo trap.
I think Zwift presents a good solution to the turbo trap, especially with a smart turbo, getting you riding far more dynamically (and more representative of outdoor riding) than you would usually do during typical turbo sessions. Just need to keep an eye on position to ensure specificity.
Edit… also…
This is a really important one that isn’t measured much. Riding fast outdoors usually involves repeated hard efforts while riding at or near your limits. Understanding how hard you can go for short durations and how quickly you can recover and do it again is really useful.