In CS6 and later the conversion of Pantone+ Solids to CMYK is color managed (Lab to CMYK), so the document's assigned CMYK profile and the app's Color Settings Conversion Options (Intent and Black Point Compensation) affect the conversion numbers and have to be matched up.
So below the assigned profile is Coated Fogra39 with a Relative Colormetric Intent and BPC turned on (the slight differences are because of the way the 3 programs round):
I think InDesign has a problem with color conversions via the Color panel, so I'm showing the InDesign Sep Preview panel with All Spots to Process checked in Ink Manager on the right. Changing the document's CMYK profile assignment doesn't reliably produce the correct conversion via the Color panel—looks like a bug and I haven't checked CC to see if it's been fixed.
Here is what I get with a conversion via the Color panel. l'm not sure where these numbers are coming from but it's not the right conversion to Fogra39:
The tool bar's Color Picker does make the correct conversion, so I think the problem is limited to the Color panel
The simplest approach is to leave Pantone Solids as spot colors and use Ink Manager to make the conversion when you export or print.
Also, depending what content you're applying that grey to, it could be better to just use the black plate, particularly if it's smaller text. 69% black looks about right for FOGRA39 here, but I don't know what your output profile is.
if it's smaller text. 69% black looks about right for FOGRA39
Yes, for perfect neutrals and certain out-of-gamut colors, a color managed CMYK simulation of a Pantone solid ink can create a bigger problem than the one it solves.
I just checked CC2014 and the Color panel is still broken. It looks like the color conversion is always to US SWOP, Relative Colormetric with BPC on even when the CMYK profile assignment and conversion options are different.