Yup, that's true. Easy to test by just casting Swiftmend and watching Lightweave proc partway through.
So you have to know how to compute what you expect a Swiftmend or Efflo size to be based on your current spellpower and mastery. TreeCalcs can do this if you just manually drop your current spellpower and mastery into the right spots in Basic Calcs (don't save after you do). Or, just go to wowhead:
Swiftmend - Spell - World of Warcraft
So you know that a Swiftmend will be (13966 + 1.29*spellpower)*(1 + Harmony). Read spellpower and harmony straight from your char sheet (take off proc effects and PvP power first). If your in-game SM amount matches that number, you know you're all calibrated. Then you can multiply that by 0.12 to find your expected Efflo tick, and it should match what you have in-game (or a few points higher for some reason, like I mentioned).
Unlike in Cata, you no longer have to multiply the Efflo tick by Harmony again to get the right outcome, and also, the Efflo size in unchanged if the Swiftmend crits.