Indeed, I retested using the following example file:
$ realpath example.tex
/home/werner/test/example.tex
$ cat example.tex
\documentclass{article}
\begin{document}
The well known Pythagorean theorem \(x^2 + y^2 = z^2\) was
proved to be invalid for other exponents.
Meaning the next equation has no integer solutions:
\[ x^n + y^n = z^n \]
\end{document}
The results show that all the methods discussed here are vaild:
NotebookPut@Import["/home/werner/test/example.tex", "TeX"]
or
NotebookPut@Import["/home/werner/test/example.tex", "LaTeX"]
or
A = Import["/home/werner/test/example.tex", "TeX"]
NotebookPut[A]
or
A = Import["/home/werner/test/example.tex", "LaTeX"]
NotebookPut[A]
See the following screenshot for more details: 
