I was reading Mordenkainen's Tome of Foes when I stumbled on an interesting turn of phrase (it's repeated often in the book and in others, but this was where I first realized it).
The Demonic Boons section lists the following trait for followers of Graz'zt (p. 30):
Joy from Pain. Whenever this creature suffers a critical hit, it can make one melee weapon attack as a reaction.
[Emphasis mine]
Meanwhile, in Xanathar's Guide to Everything (p. 46), the Mastermind rogue's Misdirection subclass feature says:
When you are targeted by an attack while a creature within 5 feet of you is granting you cover against that attack, you can use your reaction to have the attack target that creature instead of you.
[Emphasis mine]
Is there any mechanical difference between these two phrases? If something is done "as a reaction", does it not "use your reaction"? Or are they just interchangable phrases?