The Rama's Approach and Rav Akiva Eiger's Critique

The Rama (Yoreh Deah 293:3) presents an interesting, albeit puzzling, approach to this issue. He writes that one may be lenient regarding Chadash if the following Sefeik Sfeika (double doubt) is applicable. One doubt is if the grain was planted before the previous sixteenth of Nissan. The second doubt is that perhaps the grain is from a previous year. This approach appears difficult, as noted by Rav Akiva Eiger in his glosses to the Shulchan Aruch (ibid.). It seems that this is not a legitimate Sfek Sfeika since this is simply one doubt - did the grain take root before the sixteenth of Nissan or not?