Not unusual at all. Many instructors teach kata that aren't part of their "native" systems (although it may have been "native" to them before). The head of my old system was trained in the original Wado Ryu Karate system, directly under Ohtsuka Shihan, yet decided to re-incorporate much of the Shotokan system when he split off, incorporating many of the Shotokan kata at the advanced levels, in addition to adding a good bit of the Shotokan fundamentals. It wasn't unusual to see someone learning Chinto and Seisan at the nidan level, but also working on Shotokan's Gojushiho series, Unsu, etc. later on. My old Shuri Ryu instructor sometimes taught the Goju Ryu version of Suparinpei to those interested in competition, along with a couple of Shotokan kata, with the emphasis that they are separate from the core kata of the Shuri Ryu system. Those were more of icing on top of the cake.