You are correct. The DRS model shows all the hallmarks of corporate sponsorship. One is the reluctant and unprecedented bodyshell replacement program (someone outside Dapol was obviously was seriously upset by the error to have forced this through).
This is part of the reason why the TPE is appears to be in short supply. First, there was no sponsor involvement or control. Second, production was kept at pre-order levels only (or even actually reduced), this would be because Dapol would have known about the impending announcement of the Accurascale Mk5 coaches. Initially, it seems peculiar that Dapol did not increase quantities to take full advantage of the obvious increase demand. But, they would also have known Accurascale will get the colours of the coaches spot on right. This would highlight the problems with Dapols version of the TPE livery (its been commented elsewhere that there are issues and compromises). They feared the resulting outcry for replacement bodyshells would cost dearly and knowing that they were previously forced to set a precedent, they artificially restricted sales to limit the risks and losses. It was a profit on sales Vs costs of replacement calculation and there was no sponsorship to sweeten the blow.
It maybe that when they receive a sample of the Accurascale coaches they will copy the color correctly. Only then will they announce another batch. Maybe even along with replacement bodyshells? Time will tell if they try to charge for these.
Also, I think lack of sponsorship explains Dapols reluctance to produce a class 88, but maybe someone with a patented pantograph has already taken the initiative?