What illuminant and observer does Matlab assume when it reads in Lab values from tiff file?

Outside of Matlab, I made a tiff file with CIE Lab values. The software I used to make the tiff file assumes D50 for the illuminant and 2 degrees for the observer when saving Lab values. Now I would like to read these Lab values into Matlab. When I use imread, I get the error "Warning: Converting CIELab-encoded TIFF image to ICCLab encoding," and the documentation for imread says "If a file contains CIELAB color data, imread converts it to ICCLAB before bringing it into the MATLAB workspace." Here ICCLab seems to use a D50 illuminant and 2 degree ( 1931) observer. So two questions,

1) Can you confirm that imread assumes D50 illuminant and 2 degree observer, so it is consistent with my image source in this example?

2) Is there a way to read in the values without this assumption, so if my original source happened to use D65 illuminant and a 10 degree observer for the saved Lab values, Matlab would not assume it was D50 and 2 degrees instead?