if, for the particular display object in question, the primitive that corona emits is GL_QUADS then you won't get the two-triangle seam tearing. if otoh corona emits GL_TRIANGLES, then it'll tear when resulting implied-two-triangle-quad is non-symmetric and the uv-mapping requires a true symmetric quad.

(keep in mind that any single triangle has no "knowledge" of what "greater form" it may imply if other adjacent triangles are present, it textures itself based only on it's own uv's and has no access to some other triangle's far corner of an implied quad)

for the typical case of "real" 3d it doesn't matter - because the geometry is "static" (you can translate it, but typically not deform it) so if the original uv-mapping was correct, then it'll remain correct through any transform, whether it was based on triangles or quads.

BUT, if the geometry itself changes by free-form deformation (ie, by other than something like a uniform scaling, or a simple reflection) like a square turning into a trapezoid, then the original uv-mapping will be distorted. And this is what is happening (constantly) in a renderer like yours.

Suggest you draw a trapezoid on paper. Now draw one of the diagonals (say lower-left to upper-right). Now mark a dot at the true midpoint of that diagonal, that's uv=0.5,0.5. Now draw dashed lines from that midpoint to the remaining two corners (to upper-left and lower-right). Now imagine texturing those dashed lines - the top-left one runs from 0,0 to 0.5,0.5 but is a very short distance, the lower-right one runs from 0.5,0.5 to 1.1 (same delta as other) but covers a longer as-projected-on-screen distance, so clearly one will appear more stretched relative to the other. But also note that the two lines are not parallel, so they'll seem "skewed".

Now draw the other diagonal (from top-left to lower-right) and note that it doesn't cross the first diagonal at the midpoint (in fact, challenge question: what WOULD the uv be of that intersection point?) This difference in where the two implied "middles" are is what causes your problem, because the uv-mapping from all four corners to 0.5,0.5 is not equivalent. Further, that same similar situation occurs at ALL points along the diagonal seam between the triangles, and so arises the "seam-tearing" description.

Compare: a true 3d square, just tilted away from the camera to LOOK like a trapezoid. the two diagonals intersect at 0.5,0.5

(though i keep using trapezoids as an easy to visualize perspective example, similar artifacts would occur for any general quadrilateral formed from two non-symmetric triangles)