Does capitalgainstax lead to suboptimal resource allocation?

Imagine one has invested 50 in Stock A its value has raised to 100. Now I believe in the next year Stock A will stay at value 100 but Stock B will raise by 10%. If I sell and buy B I will end up with (assuming capitalgainstax is 20%) (50*0.8+50)*1.1= 99 which is less money in stocks than I would have If I kept Stock A.