yea, the only available styrene kits for recent day lambos, including diablo n diablo sv, are from fujimi. i personally don't like fujimi kits but had to resort to some due to the rarity of the kits. the worst offenders would be their seats. they have hollowed out backs so that needs to be filled up with putty since it's darn right visible after the kit is done. (might not be in lambo's case)
The reason tamiya RE-release their LP500 was because it was amongst their early release kits and became really sort after by collectors. They have been re-releasing a lot of their classic kits that made some builders really happy since we don't have to dish out or look around on ebay as much to finally build on. As slow as tamiya is on releasing new kits, whatever they eventually come up with are usally astonishing though, think carrera GT, enzo, fxx, and all those perfect fitting GTRs n NSXes.