wrote:
the ARCTAN should return the angle in degrees!
As does the TAN return the ratio based on degrees.

You are entitled to your opinion. But it would be nice if it were an
informed opinion.

In Excel, the argument to the TAN function is in radians, not degrees.

Here is the relevant information from the help page:

TAN(number)
Number is the angle in __radians__ for which you want the tangent.