That’s not what they’re asking. What they’re asking is if, when you and your opponent select a mon on team preview, if sending the mon out first has any bearing on determining its Speed. Pretty sure the answer is no.
What you can use to determine Speed is stuff like ability / item activations.
E.g. You send out a Scarf Lando-T, your opponent sends out a Tapu Lele.
Psychic Surge activates first and sets terrain, then Intimidate activates.
You can thus deduce that the opponent’s Lele is also Scarf.