Lambet-Beer's law does not predict linearity only between 0.1 and 1.0 absorbance. It is a standard practice and true linearity will depend on the spectrometer. For example Shimadzu claims its UV-2700 model has linearity up to 8 absorbance value.

https://www.ssi.shimadzu.com/products/literature/Spectroscopy/C101-E121B.pdf

Though I am really surprised by the value of 300 (I had to confirm myself) it does not speak of  linearity.  Most importantly the absorbance value is reported for 10 mm pathlength though the pathlength available is only 1 or even 0.05 mm. Thus the spectrometer actually measures an absorbance value of 30 (not 300) for 1 mm pathlength. If you consider 0.05 mm pathlength the absorbance is less than 1. This definitely does not look like high absorbance.

http://www.nanodrop.com/Productnd2000specs.aspx

http://www.nanodrop.com/library/NanoDrop%201000-linearity-Performance-Data.pdf