That is my guess as well. It seem to usually work that way. I was kind of surprised by the flash price hike. Almost $800 for the MT-24EX macro flash seems a bit absurd, especially since it is quite outdated technology. Nikon's far superior wireless macro flash system is significantly cheaper.
I wonder if you've used the Nikon system? Firstly of course Nikon doesn't have a competitor to the MP-e 65mm so it's sole use is for Macro, and it seems an awful lot of money to spend when you can illuminate with a conventional flash.
The other issue it has is two flash heads which both need independant battery power this is provided by very expensive non rechargeable Li specialised units, it also means the heads are much larger and weigh! This flash system absolutely cannot be used with extending lenses like the Sigma or Tamron as the focus motor will burn out. They struggle with the relatively lightweight Canon system.
I tried (& failed) to find a guide number for these units, but Nikon don't seem to quote one, several sources say it can only be used for macro, so I assume that they aren't very powerful.
Be careful what you wish for! At first sight Nikon might seem to have a better system, but when you dig a little deeper it's not all it appears to be.
I'm quite happy with the MT24-EX replacement to remain wired & high power, with conventional AA rechargeable, & the tech inside like the 580EX II (or III)