That
is the point of a TPM. They're supposed to be the neutral third party that makes sure you're doing the work, and can explain to upper management why the work is not getting done. As such, they don't have any decision-making power on
what the work is or
how long it's going to take. Generally the manager and IC negotiate back and forth on what needs doing and on what schedule, they set their own deadlines based on the realities of the project, and then the TPM holds them to what they committed to.
Much of the reason the TPM job exists is simply so your manager can be an advocate rather than a nag. The nag job is offloaded to the TPM, but the TPM has no decision-making power, so you don't get perverse incentives where the manager burns all their relationship capital making you do your work, or sandbags the deadlines so they don't have to.
In many orgs TPMs are also in charge of goodies like fun events or device/swag distribution, as a way to offset the negative emotions that come from them basically being nags.