Still, if you reported the 2018 RMD taken in 2019 as income on your 2018 tax return, that was a mistake that you must correct by amending your 2018 tax return. The IRS won't complain about you reporting on your 2018 tax return income that was not actually income received in 2018 but will certainly object to you omitting this 2019 income from your 2019 tax return.
