TLM roles are a trap, but not in that sense. There's no expectation that you do two jobs at once.
It's just a way to ease unsuspecting engineers into management. If you don't suck at management, your team inevitably grows (or you're handed over other teams), and before long, you're managing full-time.
Which means that there are three type of people who remain TLMs in the long haul: those who suck at management; those managing dead-end projects on dead-end teams; or those who desperately cling on to the engineering past and actively refuse to take on more people. From a corporate point of view, none of these situations are great, hence the recent pushback against TLM roles in the industry.