probably yes to manage customer expectations, the BT wholesale checker has absolutely no bearing on your contract with talktalk, the estimated speed they gave you at signup does, but that can be anything of their choosing although they tend to use the estimate information provided by BT as a guideline.
So as an example if talktalk estimated 40000kbit sync speed, BTw estimated 60000 and you got 45000, then you got little to back you up on a performance related fault as you still 5000 above what talktalk told you.