I can't really object on principle to the use of a bi-pin bulb in an application like this. On one hand, it's not a prefocus base (that's the "P" at the start of all the official headlight bulbs' base designation...P14.5s for H1, PK22S for H3, P43t for H4, PX20D for HB3, etc.). Without a prefocus base, it would not be suitable for creating a low beam pattern. But on the other hand, the Fyrlyt lamps appear to have a focus adjustment that shifts the bulb to tighten or broaden the high intensity region of the beam, so a prefocus base is not a crucial need. One factor that might lean toward using something like a G6.35 bipin base is very low bulb weight, which would tend to make the bulb relatively resistant to troublesome movement and vibration in service.
Much though the phrase is abused and misused a lot, there really is such a thing as a lamp designed and intended for "off-road use only" (which has to include unregulated roads, such as the ones that run through empty deserts). In designing such a lamp, there is no airtight reason to confine bulb selection to those approved for legally regulated lamps. There is the potential pitfall that if Osram ever discontinues this purpose-specified bulb then owners of these lamps will be forced to substitute bulbs that will probably fit and work but with possibly less satisfactory characteristics (lifespan?) but other than that, for this application with those bulb specs I'm not seeing a problem.
Avoid the trap I tripped over: Fyrlyts are not the same as Lightforce.