Sorry that is absolute rubbish. First you are completely wrong in than anyone with two neurons to scratch together or even rudimentary investigative skill can show your first premise is complete rubbish. You second premise has nothing to do with the price of fish, or the question at hand for that matter. There is no analogy between tar and either encryption or compression. All tar does is glue files together with just enough header data to split them back into a dir structure and check for corruption.
I have presented some sample code above. Please experiment with it and follow your own suggestion. Please learn from it as you clearly have NFI.
As noted you will get >>>>>ZERO COMPRESSION<<<<< if you encrypt first with any decent algorithm. By design an encryption algorithm will turn an infinite stream of zeros into an equally infinite stream of (pseudo)random noise. This can not, by definition, be compressed. This is not a bug. This is by design :-)
If you can compress your encrypted files I suggest you have a problem with your encryption algorithm.