All is not lost! If you fill the inside of the 'X' with an empty fill, it should nullify the polygon count issue.
True, that magic-wanding a will will get rid of the polygon count issue most of the time. (Not all of the time, as it seems that some times magic wanding a curved area results in a curved fill that does not precisely align with the original - depends on magic wand settings/etc.)
But, there are other reasons to do it the way I illustrated earlier in this thread with four triangles using 2 different fills - the hotspots / lines are in the 'right' location if you need to dimension any enlarged wall sections/etc.
Like everything else in modeling - I just think it is best to do things precisely to avoid any possible issues later. Creating linework in section via minuscule gaps, even if zoomed in and filled with another fill, is just asking for problems down the road, I think. 😉
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