How do you think reducing heat reduces the lag?
A turbo works by compressing air and forcing it into the combustion chamber. The more air between turbo and chamber, the longer it takes to compress that air. Wrapping of the exhaust will not make any difference to the lag, only help to reduce intake temps in the engine bay, a feat which is better accomplished by intercooling or chargecooling. No harm in wrapping at all, but it won't benefit the car in the way you think.
You won't be increasing the lag a bit, you'll be increasing it massively by a factor of however much longer rear mount pipe work is to front mount. I'm guessing at at least twice as much, more likely three or four times.
Keeping the gasses hot spins the turbo faster apparently. Some "race" cars wrap front to back since hot air travels faster.
You could be right and in theory you are 100% right but unless you have tried it on the car you don't know how it will be.