A room can be acoustically dead yet not anechoic, with early reflections surviving.

Evidence

However, although they are quite dead acoustically, they are not anechoic. Because for users in the room there are some reflections from the hard surfaces, there are some early reflections that make the room nonanechoic. However, sound that is emitted from the speakers is absorbed and is never able to contribute to the reverberant field. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2303

Categorization

• DEFINE: Clarifies the crucial distinction between a ‘dead’ (low-reverberance) room and a truly anechoic one, a distinction easily collapsed in everyday listening talk.
• XREF: connects to: Non-environment rooms kill the reverberant field while keeping early reflections for occupants — David Howard, Jamie Angus, coustics and Psychoacoustics, 2294