Andy Murray's racket
 

I heard sometimes when Andy wants more control of the ball/ strokes during the match, he will switch from PT57 (16x19 pattern) to TGK 231.2 (18x20 pattern).

Is it true?

No, its false. He plays with one frame PT57A with 16x19 string pattern.

I also heard that E Bay posters/sellers can be full of crap...

Probablly^

If it's on the internet it must be true.

^ Life's only guarantee

If this logic were true why wouldn't he switch to a normal PT57?

According to that guy, he said Andy Murray places a few TGK 231.2 in his bag as back ups. For example, during a match, if he needs more control on the ball instead of power.

Anyone can confirm??

It was already confirmed for you in the post #2. How many confirmations you need??

Nope, I saw that racket for sale also on the bay, that would've just been in his bag as head send him whatever he requests.