HP Prime bug for approximate(erfc(z)), z as (0+b*i), or erf(b*i)

[Gil]

Try for instance on the HP PRIME approximate(erfc(5*i))

ie with no real part in the complex number input (argument).

It returns -82982738 79.76*i (a complex number with no real part).
According to Wolfram Alpha, the result should be
1 - 8.2982738 806 7680 ×10^9 i
(with the number 1 as the real part of the resulting complex number).

Fazit
1) As no real part of the HP PRIME result is shown, that part has to be considered being equal to 0, and the PRIME result seems therefore clearly to be wrong here (a bug?).
2) As a basic program on the HP50G allows to find (1.,-82982738 80.61), we see that the imaginary part of the HP PRIME is not so well "calibrated", letting suppose that the internal algorithm of the HP PRIME for erfc function could or should be improved.

Logically, on HP PRIME, approximate(erf(5*i)) returns
1 -82982738 79.76*i (a complex number with the number 1 as its real part, instead of 0).

Strange.

Or did I miss something?

Regards

Gil