The whole idea in any uncooled infrared detector is to have a good thermal isolation between the absorber and the substrate.
However, when we make the thermoelectric wires very long and thin, we also lower the natural resonance frequencies of the structure. This might be a problem if these resonance modes have frequencies close to the detector working bandwidth. Why? because silicon is a piezo-resistive material. When the detector starts resonating, it will generate undesired signals in the output. If these unwanted signals cannot be filtered out, then we are in serious problem.