“sparse files” are specific term[1] referring to files where the filesystem tracks and doesn’t allocate space for unwritten file content (i.e. content that would just be zeros if read) in large preallocated files.
To use the term “sparse file” to also refer to files with large continuous runs of zeros, created via a seek operation, is just confusing. Those are quite explicitly not sparse files, they’re just files, that happen to be full of zeros (all written to disk). “Sparse file” are quite explicitly the result of the optimisation to avoid writing pointless zeros when preallocating a large file that’s going to written into in an unordered manner.
Using the term “sparse files” to refer to both the “problem” and the “solution” is just unhelpful, and doesn’t align with the accepted meaning of the term.
[1] https://en.m.wikipedia.org/wiki/Sparse_file
