The 20-year-old Swansea-born London Irish fly-half or centre was named as one of six uncapped players in Robinson's 36-man squad as preparations for the February 4 Calcutta Cup clash with England at Murrayfield began in earnest.
Scotland coach Andy Robinson believes Shingler qualifies as a result of his Dumfries-born mother.
However, Shingler played at full-back for Wales Under-20s against France Under-20s in the 2011 Six Nations, when both nations declared the age-group squads as their second XVs, effectively handcuffing the players involved to those nations.
A statement from the Welsh Rugby Union read: "The WRU complies with IRB (International Rugby Board) regulations and guidelines regarding the status of potentially Wales qualified players who are selected at elite pathway representative level.
"The Wales U20 team is currently the WRU nominated side for qualification which means that players who represent Wales at this level in certain games are then solely qualified for Welsh senior honours.
"All Welsh players who represent Wales at U20 level against nations which also designate their U20 teams as their qualification sides are informed that they will then be registered as liable for Wales selection only at senior level.
"All the U20 players who represented Wales against France at U20 level in 2011 were informed that they would then become Wales qualified players only at senior level."
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