Because of the added sanity checks in rB14508ef100c9 (D11492), seeking in proxies would not work correctly any more.
This is because it wasn't working as intended before, but in most cases this wouldn't be noticeable.
However now when the sanity checks are tripped it is very noticeable that something is wrong

The indexer tried to use dts values for time stamps when we used pts in our decode functions to get the time positions.
This would make it start in the wrong GOP frames when searching. Now that we enforce no crossing of GOP frames when decoding after seek, this would lead to issues.

Now we correctly use pts (or dts if pts is not available) and thus we don't have any seeking issues because of time stamp format missmatch.