Why is unit: strain not equivalent to unit: dimensionless?

Created by: ecm0

signal is from SimInspiralTD noise is from fetch_open_data

>>> print(signal, noise)
TimeSeries([-0.00000000e+00, -1.18056766e-35, -4.85012196e-35,
            ..., -7.31937230e-36, -3.88448335e-36,
            -1.12604229e-36]
           unit: strain,
           t0: 1187008881.988265 s,
           dt: 0.000244140625 s,
           name: H_PLUS,
           channel: H_PLUS) 
TimeSeries([-2.07535931e-17, -2.07549921e-17, -2.07426622e-17,
            ..., -2.30985486e-17, -2.31243374e-17,
            -2.31374493e-17]
           unit: dimensionless,
           t0: 1187008877.0 s,
           dt: 0.000244140625 s,
           name: Strain,
           channel: None)
>>> signal.to(noise.unit)
UnitConversionError: 'strain' and '' (dimensionless) are not convertible