This paper documents a fundamental architectural incompatibility between C++20 symmetric transfer (P0913R1) and the sender model of std::execution (P2300R10). Sender algorithms compose operations through non-coroutine struct-based receivers with void-returning set_value, making it structurally impossible for await_suspend to return a coroutine_handle<> and perform a tail call, which prevents constant-stack coroutine chains when co_awaiting senders. The paper argues this gap is not a missing feature but an architectural consequence of the sender model's design choices, inherited by std::execution::task (P3552R3), and that available mitigations such as trampoline schedulers reintroduce the runtime costs symmetric transfer was adopted to eliminate.