If they were uncut sheets there would not be 15 of one player and none of another. This is what a related E93 sheet looked like.
The two sets share several of the same player images. I think it is fair to assume that like the 30 card E93 set, the E98s sets were likely printed all on one sheet. Apparently the cards were found in a box bundled and tied in groups with twine according to the description on the Heritage site.
And as mentioned, the high res blowup scan reveals dot patters identical to known E98s and virtually all 1910 era lithography. According to experts it is a pattern that would be extremely difficult and costly to duplicate today. I think the likelihood that they are not real is almost zero. Just my opinion.
JimB