LR, yes. ACR, no. ACR uses the colour space (and associated gamma) of whatever is chosen as the output space in the Workflow Options at the bottom of the screen.
Whatever "is chosen as the output space
" is exactly that - output
space - internally
it is prophoto and there is some math there in ACR/LR between the raw data and whatever is actually pushed by the exposure slider.
Eric Chan, for example (one of many) = "...the internal reference scene-referred space in Camera Raw & LR is indeed RIMM (ProPhoto linear)..."
For some other non core operations (but not the exposure correction) there might even further (errors, errors) conversion (prophoto/linear -> probably some modded form of the output space selected).
Eric Chan, for example (one of many) = "...The actual color space used for an operation depends on the routine (e.g., noise reduction, clarity, fill light, HSL adjustments, etc.)....", "...ACR/LR does perform internal color transforms as needed to carry out its various image processing routines (e.g., noise reduction, vibrance, etc.). However, this is all done internally and has no real connection to the user-specified color space of the rendered output file (e.g., sRGB, Adobe RGB, etc.)...."
/ added - one more curious detail found = Eric Chan :: "ACR does use L*a*b* for some internal color difference estimates, e.g., for auto-calculated masks."
but the first thing ACR/LR do - is to get rid of the raw data by converting that to its internal space - once and only once
What commercial converters do allow you to work directly on the raw data?
Why do you try to limit yourself to commercial software ?