Dear @rbavery,
In Sen2Cor v2.11 a saturation at 25% of surface reflectance is used to generate the L2A TCI.
Meaning that a pixel with a surface reflectance of 25% (or higher) will be set at 255 in the 8bits image.
Please note that the official L2A TCI generated by ESA uses a software component external to Sen2Cor. It is the same software component used to generate the L1C TCI, with different configuration parameters.
A previous answer is available here: What is the valid range for the TCI product? - #2 by TomAugspurger
We may add this information to the Sen2Cor Frequently Asked Questions.
Cheers,
@Sen2cor_dev_team