How is the data of special Missingno determined?

Question

This is a kind of special MissingNo in gen 1
And what does bulbapedia say about these guys?

These Pokémon have no constant base stats, experience types or starting moves; instead they take this data from the last Pokémon in the party other than another special MissingNo.

But bulbapedia also says:

it will use the type of the Pokémon whose data was accessed last, just as it will share the leveling up learnset, base stats, and types of it.

So which one is it? Is it the last one used, or the last one is the party?

FOLLOW UP
If it’s the last one in party then what if it’s the only one in the party? Or if it’s the last one?

If it’s the last one used then what if you only ever used special Missingno (like what if you started with one as your starter)

Comments

why would when you send it out affect it? if it's based on the pokemon in the last slot in the party, shouldnt the question be what happens if it's the only pokemon in the party?

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Ohhhhh I thought it said the last Pokémon SENT OUT. Oops. Changed question

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considering the bulbapedia page you linked says " it will use the type of the Pokémon whose data was accessed last, just as it will share the leveling up learnset, base stats, and types of it." i would imagine it uses those of the last pokemon you used.

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So it is the last one sent out? I’m confused…
EDIT: changed question again