Thank you for the file. When you export TIFFs in the "RGB render" mode, autoscaling ("Autoscale to use full 16-bit range") is applied by default. That may be good for previews, but not for analysis, and especially not for clipping analysis.
To switch autoscaling off, please go to RawDigger preferences, "Display options", and switch off "Automatic exposure correction for RGB render" (page 44 of the manual). If raw isn't clipped and the clipping point ("white level") is set correctly, RawDigger will export a 16-bit TIFF without clipping. In this mode, 78 pixels are clipped in Photoshop 255 histogram limit if the RawDigger export is set to sRGB (default), 15 if it is set to ProPhoto RGB in preferences ("Display options" - "RGB rendering color space", page 43 of the manual). Photoshop rounds 16-bit files for the purpose of displaying histograms in 8-bit mode.
If you look at the distribution in ImageJ (a very useful image analysis tool, en.wikipedia.org/wiki/ImageJ ), nothing is clipped in the TIFF, here is the extreme highlight portion:
244 62463 57
245 62719 37
246 62975 34
247 63231 35
248 63487 45
249 63743 25
250 63999 31
251 64255 31
252 64511 13
253 64767 11
254 65023 1
255 65279 17
The 16-bit limit is 65535, but the maximum is 65279, that is lower.
Also, in Photoshop, use "Set foreground color" to set it to 255, go to "Select" - "Color range", choose "Sampled colors" as the mode, press OK, and Photoshop will prompt "No pixels selected", meaning the pixels at exact 255 value are absent or so few and scarce that Photoshop can't isolate them.
RawDigger TIFF export is not of a general raw converter, it is an instrumental one, like the other functions in RawDigger.