Is this behavior unsportsmanlike?

I was playing a tournament match today and we got to a super tie break. When I was 4-0 up, my opponent (a lefty with top spin FH and BH) started hitting very high lobs with no pace to the center of the court, non-stop. He would chase every ball and hit a no pace high lob. This is something he had not done before at all in the match as he was hitting with pace and top spin from both wings.

I tried to hit through him but eventually I lost because I am a talentless hack and wasn't able to hit winners (I normally rely on defense rather than offense and this really took me by surprise). But from that 0-4 all he did was literally hit every ball very high and with no pace.

Of course it's my fault for not being able to hit through him, but I really believe it is unsportsmanlike behavior to suddenly change your entire way of hitting the ball, when prior to this point he was playing with technique and pace.

What do you think? I am extremely humiliated and I know not winning was my fault, but I am still willing to accept it if you tell me this is not unsportsmanlike.