The capacity in OTSM cap is sensitive to voltage and temperature like with OTC, but it’s irrelevant because the timing is precise.
Think of a cap as a bucket of water. Turning off the flashlight is like draining the bucket.
OTC: When the flashlight is off you are draining water at a quick but unknown rate. When you turn the flashlight back on you try to find out how much water was drained by looking at how much is left in the bucket, but because you don’t know how much was in the bucket to begin with you can only estimate.
OTSM: When the flashlight is off you are draining the bucket at a much slower rate, but more importantly you are also measuring exactly how much water is being drained. When you turn it back on this exact number is available to you.
OTC works well enough for single short off presses. People have been doing this a long time, it works pretty good. In the above example it’s like simply checking if there is any water left in the bucket at all. But if you are going to time both short and long off presses it can be difficult. Have a look at this thread, and check out the results in post #15: Off-Time Memory Dependent On Altitude? - Resolved!. Try to reliably measure 1.5 seconds long off time presses with that light and you’ll run into problems.