Well... no, that really doesn't work out.
That Shirou was Tracing for so long (and that, basically, his entire magical system was based upon it) is the reason why UBW developed. While not completely correct, you could say that Reality Marbles are externalizations of ones soul (not really, it's more like they're external materializations of their inner works instead of their soul, but even that is sort of...). Regardless, what I'm saying is that if Shirou hadn't even touched upon Tracing until that point, then he very likely wouldn't even HAVE a Reality Marble on the rise, or if he did, it wouldn't be UBW (Unlimited Rin Works? lawl).
Of course, if you base the war with just a bunch of Rin, there's no real reason for Shirou to even HAVE UBW, so it's kind of moot.
That Shirou was Tracing for so long (and that, basically, his entire magical system was based upon it) is the reason why UBW developed. While not completely correct, you could say that Reality Marbles are externalizations of ones soul (not really, it's more like they're external materializations of their inner works instead of their soul, but even that is sort of...). Regardless, what I'm saying is that if Shirou hadn't even touched upon Tracing until that point, then he very likely wouldn't even HAVE a Reality Marble on the rise, or if he did, it wouldn't be UBW (Unlimited Rin Works? lawl).
Of course, if you base the war with just a bunch of Rin, there's no real reason for Shirou to even HAVE UBW, so it's kind of moot.