The principal tectonic processes (ridge building, subduction, etc.) responsible for changing the ocean basins are measured in millions of years and are so slow that short-term global satellite records do not consider them. Glacial isostatic adjustment is comparatively a much shorter-term process (although still measured in thousands of years), and it does have a minor effect on ocean basin size. The current effect has been estimated to be -0.3 mm/yr of equivalent sea level rise due to increasing ocean basin size. This effect is corrected in the satellite altimeter global mean sea level time series and contributes 0.3 mm/yr to the estimated global mean sea level. This is considered a small effect since it is less than our estimated error of 0.4 mm/yr.
For further information see the reference "Sea Level Variations over Geologic Time."