Invulnerability Effect of Zelda/Sheik's Transform

My friend and I have been arguing about whether or not using transform grants any sort of temporary invulnerability to attacks in Melee.

According to the wiki, invulnerability occurs because the game has to load the characters. However, the wiki states that for Melee specifically:

In Melee, both Zelda and Sheik are loaded in the game's memory at all times, allowing the transformation to occur instantly with no loading required.

This would lead me to believe that no such invulnerability exists when using transform in Melee, though my friend still adamantly claims to have used the transform ability to dodge attacks.

1) Does this invulnerability work in Melee?

2) If it does not work in Melee, what are its mechanics more generally in the Super Smash Bros series (eg how many frames are you invulnerable, how useful is it in practice, etc.)

I'm happy to make this 2 separate questions if necessary, though I think they are sufficiently related to allow them both being tackled here.

1) Yes. Both Zelda's and Sheik's Transform have intangibility frames in Melee. Zelda's transform provides intangibility on frames 34-43, while Sheik's transform provides it on frames 27-36. Sources here: Zelda frame data, Sheik frame data.

Note that intangibility is different from invincibility; intangibility means that the hurtboxes (in this case, the entire player model) do not interact with any attack whatsoever. This is different from invincibility in that invincibility means attacks will interact and cause hitlag on the attacker, although with no damage or knockback.

2) Brawl is the only other game to feature the Zelda/Sheik transformation (the feature was removed and replaced in Smash 4). Both transformations also provide intangibility.

However, in Brawl the time is not fixed, because the character that you are transforming into must be loaded from the disc while the animation plays. This can be seen if you eject then reinsert the Brawl disc right after starting Zelda or Sheik's transformation; the transformation takes a much longer time to perform due to the disc error, and you are intangible for the entire length of it.

Overall, though transforming does provide intangibility in both games, it is not an efficient way of dodging attacks in practice. The animation itself is quite slow and leaves you very vulnerable and unable to do anything before and after the intangibility frames.