Hi Jimmy - I think a flanking line tornado is exactly that - I assume it to be a general term for any tornado that occurs under the flanking line. I'll stand corrected if it refers to a particular process going on under the flanking line, and if so I'm not familiar with it. I would have thought that the majority of tornadoes that occur under the flanking line would be classed as landspouts since new updrafts would provide a good opportunity for vortex stretching?
So, to answer your question, no, since they are describing things at different levels. Actually, it is probably worth clarifying a few things starting at the top. It seems the basic distinction is made between mesocyclone and non-mesocyclone tornadoes. Well I would assume this sort of nomenclature places emphasis on the former being, generally speaking, a much greater risk to life and property. A non-mesocyclone tornado, of which landspouts are a type, by their very definition occur not necessarily in the absence of, but more or less independently of the dynamical process that is a mesocyclone. [ as an aside, the Jarrel event might imply that a single tornado under a particular set of conditions might be borne as a non-mesocyclone tornado and, as the storm-scale processes evolve (-> supercell), make the transition into a mesocyclonic tornado (that is as soon as the tornado was the product of a low-level mesocyclone, even though a tornado was on the ground preceding meso formation!). At the other extreme, in the case of some rope-out phases (think about May 12, 2004) the tornado appears to be on the ground even though the fully occluded meso is probably no longer a mesocyclone at all by all the standard criteria - does it then become a non-mesocyclone tornado during the process of it's demise,,,,,, anyway that's pretty ridiculous].
The point being, a whole bunch of dynamical processes are lumped together (eg landpouts, coldies) as non-mesocyclone tornadoes. A landspout would appear to favour an environment where an updraft can stretch pre-existing vertical vorticity to produce the tornado - the normal situation here would be an environment characterised by some sufficient amount of low-level CAPE and a existing surface boundary to serve as a source of vertical vorticity. This occurred on May 24, 2004. While, yes, there was a mesocyclone that produced at least two mesocyclone tornadoes, the other tornadoes that formed under the flanking line did not require the presence of that mesocyclone per se (of course one could say that they in fact did in that the flanking line would not have existed if the supercell did not exist but, as Dr Chuck Doswell would say, that is reductio ad absurdun
)....you get the drift. So, in summary, the tornado in question was possibly a landspout - this would imply the fortuitous co-existence of the ingredients mentioned above - the thermal boundary that you noted would imply there was pre-existing vertical vorticity in the region. If it wasn't a landspout, perhaps it may have developed along the RFD as the anticyclonic member of a vortex couplet --> Read Chuck Doswell's essay as linked below.
I'll be interested to read your report buddy I wish we had more time to view that piece of video and discuss it!