I'm pretty sure this isn't accurate. It's only the number of inputs that matter as DrinkingFood said.
Also Tap DI is not a thing. You can Smash DI with both the joystick and the c-stick. Smash DI is when you smash either stick during hitlag (so when you freeze in place before you launch). There is no hitlag when you are grabbed, so Smash DI is not a thing for grabs (or throws actually, except for jigg's f-throw afaik). Smash DI simply moves you a set distance before launch. There is also Automatic Smash DI which is a bit different (and easier). It also moves you a set distance, but it doesn't do it until a frame after you start launching from knockback and it moves you less than Smash DI iirc. You can do this simply by holding the joystick or c-stick. For both Smash DI and Automatic Smash DI, if both the joystick and the c-stick are used that the same time, it will only read the c-stick (in other words. the c-stick takes priority). This is useful, since for normal DI it only reads the joystick, so you can easily do Automatic Smash DI and normal DI on the same hit.
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artofskjet
It could be a glitch... The two ways I know this can happen that are known are:
-if you are grounded and platform rises lifting the person you grabbed away.
-if Pokemon Stadium transforms when someone is grabbed, the grab will break (I think regardless of where you are on the stage).