If I understood right, in this way you loaded two different Xvesa versions from cpio archives to different paths in the initramfs, which is an unforeseen case.
Besides from using separate tce dirs as gerald_clark suggested, loading the cpio archives via bootparam initrd= from a different path (e.g. where tinycore.gz resp. microcore.gz are located) would give most control, also in specifying the order of loading.