If see no issue, then maybe better not to read further - ignorance is bliss 
If you have expert setting on then will have a new UI option:
Video Frame Manager Map for Stream Type Single under Settings -> CoreELEC
You can remove the deinterlace from that string when playing (~24p) content under h/w decoding.
At a casual glance it may appear fine with deinterlace in the string, but infact it is only showing half the horizontal res, clear examples below from intro text on VC-1 Rush Hour, stairsteps on the A and the clarity of the large text below clearly show the issue.
with deinterlace:
without deinterlace:
So the H/W decoder is actually fine it is working the same in both cases, but with deinterlace in the vfm map it well “deinterlaces” the decoded progressive content and get half the detail, with deinterlace removed it is now correct but has a new problem a slow frame rate.
Pure speculation:
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Something thinks the frame rate should be halfed and is outputing as such - i.e. something thinks all VC-1 is interlaced later in the flow maybe though at that point kinda irrelevant what the original encoding was, just video then.
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The pipeline for the older decoder just is not good enough for the volume of video data at the final stages and cannot keep up (seems unlikely but looks like there is a special lossless compression applied for newer modes of operation of the video pipeline - likely to deal with bandwidth limitations probably for things like 4K and later on 8K)