I'm also facing this problem in my model's development, currently, I'm using the Thin Plate Spline (TIN) algorithm as a replacement for QGIS' native TIN algorithm or the Multilevel B-Spline depending on my needs.
I think you should post a bug report as that's not the intended behavior.
See https://github.com/qgis/QGIS/issues/30029, as of 3.22.11 LTR this bug hasn't been resolved, the workaround is using SAGA TIN for a drop-in replacement (albeit with different result compared to the native algorithm).
Edit: I'm currently using
Triangulation [saga:triangulation] from SAGA (https://saga-gis.sourceforge.io/saga_tool_doc/7.8.2/grid_gridding_5.html), which need a point layer. So, as an intermediate, I'm passing the vector layer to
Vector geometry -> Points along geometry [native:pointsalonglines] with 2m spacing. Both works in model builder and result in an otherwise identical result (to the naked eye, and in my case, after converting back to contour line) to