I'm 99% sure this isn't true. Can you point to a single paper that mentions it?
Edit: actually I'm 100% sure this isn't true. See for example the all sky map from planck (http://www.bbc.co.uk/news/special/2013/newsspec_5106/img/pla...). And a paper discussing how they will measure the CMB dipole using planck https://ui.adsabs.harvard.edu/abs/2002A%26A...393..359P/abst...