If it works, then it’s better to complete the interval. I don’t think 80-85 is especially low. I’m naturally about 90-92 inside, and about 92-94 outside (but then outside rides tend to be lower intensity).
One observation, are you a bigger (as in taller and stronger, not as in fat!) guy?
I’ve noticed that (as a very general rule) the big, strong rouleurs and TTers tend to push higher gears at low cadence, while the climbers and puncheurs tend to spin a bit quicker.