The Soulbond ability represents a couple of very long and wordy abilities:
When this creature enters the battlefield, if you control both this creature and another creature and both are unpaired, you may pair this creature with another unpaired creature you control for as long as both remain creatures on the battlefield under your control
Whenever another creature enters the battlefield under your control, if you control both that creature and this one and both are unpaired, you may pair that creature with this creature for as long as both remain creatures on the battlefield under your control.
Suppose I want to make a card with Soulbond, but I want to give it a way to pair with creatures other than these two ETB triggered abilities: specifically, I want to give it an activated ability that pairs it with something. I'd need to recreate Soulbond's rules text for the activated ability, but that's quite a lot of text to put on the card.
Sometimes, however, rules text is deliberately redundant just for clarity's sake — for example, Ashcloud Phoenix had a few words added to its first ability that only served to remind players of what the rules already did — so maybe not all of those words are strictly necessary, and just add clarity.
Under current rules infrastructure, if I'm homebrewing a card that has Soulbond and an activated ability that pairs it up, how much of the Soulbond boilerplate can I drop from that activated ability's text?
Or in other words, are these all functionally equivalent? At what point have I taken out enough that I've fundamentally changed the nature of Bonding? (Assume these are on a creature with Soulbond.)
Full template:
{T}: Choose a creature you control. If you control both the chosen creature and {this card} and both are unpaired, you may pair the chosen creature with {this card} for as long as both remain creatures on the battlefield under your control.
Dropping most of the "if":
{T}: If {this card} is unpaired, you may pair an unpaired creature you control with {this card} for as long as both remain creatures on the battlefield under your control.
Dropping the "as long as":
{T}: If {this card} is unpaired, you may pair an unpaired creature you control with {this card}.