Well, I'm afraid you just may have to try one, it would probably be good if you were able to find a place to sell you ONE coil, that would probably be a B&M but if you can acquire one you can fin out. You won't damage the tank trying one or anything, provided you are reasonably gentle with it
To me that sounds like a "We want you to buy the expensive coils for our tank that we didn't even design ourselves kind of response, frankly. It doesn't sound like anything I would accept as necessarily 100% fact.
If you know someone who uses those coils in your general vicinity maybe you can try one. If I used those coils (unfortunately I don't) I would send you one so you can find out, a coil in an envelope is pretty not expensive to put in the mail, but I don't have those coils. Etc.
Good luck figuring it out!
Anna