I will suggest that this was once discussed and PTC weighed in on the discussion.
If my take-away was correct, the idea that the metric equivalent would represent a value larger than the primary dimension tolerance value, this was not allowed. So they err on the side of caution by reducing (always) the tolerance by truncating rather than rounding.
I am sure ASME has also discussed this and from what I remember, the implementation is in compliance with ASME recommendations.
Yes, that description of the background is correct, and the truncating is intentional. The idea is a valid proposal, with a detail setup option as the user-configurable setting; it may be contrary to standard, but if enough people want it that way for their company, it could be done.
I agree that this should be a "configurable" option to ease/speed drawing preparation.
Regarding the dimensioning practice, so long as it follows ASME Y14.5 section 1.5
About rounding, this is also covered in section 1.6.4 acknowledging (1994) ANSI/IEEE 268 / (2009) IEEE/ASTM SI 10 rounding of US Customary linear units.
As I would make the understanding of the dimension shown, making the assumption that units are disclosed on the drawing (metric [inch]), that the secondary units are treated as reference and should not be used in the qualification for the feature and are provided as "information only"
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rather than truncating.