Sandbox Exchange rates appear (very) wrong

It seems as though, not matter the original currency used for an expense,
the converted “native” gross value appears to be far lower than it should
be (based on my tests on a GBP native currency).

For instance $100 USD is being converted to £10.02 instead of £60.00. (€100
is similarly being converted to £14.37)

This is showing up regardless of whether the expense is added via the API
or directly in the sandbox web site.

My concern is obviously whether this will continue into the production
system, or whether im missing some piece of the puzzle that isnt documented

Can anyone verify this is happening to them or offer an explanation for why
its happening?