On the case of the Levellieurs, shield spells seem to be more common AND potent in Sharlayan, since we've seen Y'shtola use a different version of Collective Unconsious (as a CNJ, even!) that stops attacks completely, the Levellieurs version of "Sacred Soil" may not even be the SCH skill itself but a Sharlayan variant (as for HOW the Sharlayans knew about it...well, that's their whole shtick, gathering knowledge and then not telling anyone about it, at least until grandpa Louisoix rebelled) or a completely different spell that works similarly.