This is a mistake in the error message of INTERP3. The error message received should say: "Data is in NDGRID format, MESHGRID format is required" instead of "Data is in MESHGRID format, NDGRID format is required".
The INTERP2 and INTERP3 functions require a sample input grid that is in MESHGRID format and the INTERPN function requires a sample input grid that is in NDGRID format. In case you want to interpolate data in NDGRID format, the INTERPN function is recommended.
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