Just lurking at mora.jp website, singles with 6 tracks with AAC-LC 320 kbps format is usually sell between 926円 to 1,234円, with each track price is 257円 (usually it will sell cheaper than the physical CD version). Yet the FLAC 96.0Khz/24bit is sell for 540円 each track, and the 4 tracks bundle (for example,
miwa latest single)) is sell for 1,600円 (which is a bit higher than the physical CD release).
If it only released on mora.jp first, the physical CD sales will not really affected, assuming the price is only a few cheaper than the physical CD with higher quality. And you'll also getting the booklet, CD, maybe a poster, and something to "touch".
But, that's only IF avex didn't release the Hi-Res audio a week earlier. People who think about audio quality will thinking about buying the Hi-Res audio even if it priced more and doesn't mind if they'll not getting the booklet and others.
And then, the case will be really different if avex also release the single on the iTunes a week earlier, and worldwide. The price is cheaper (1.25USD/7000 Indonesian Rupiah/250円 each track), and the files bought from iTunes is much easier to share than the DRM protection from mora.jp files. If this happen, the single physical sales really doomed.
Personally, I'd like to see if the physical CD sales is also good on the chart. My suggestion for avex is just release the Hi-Res Audio weeks later if avex want to rape their fans' money more. Also, release the digital music on the same day with the physical CD release without earlier announcement, not week earlier.
This kind of strategy has been used by sony to make their favorite artist's physical single sales dropped drastically on chart (LiSA and SCANDAL for example).
Unless ayu will make a special handshake event for 30,000 people at once, and the handshake ticket was on the CD's first press release.
Only avex and ayu know their best decision. In this kind of era, not so many people will bought physical CD except for quality and collector-wise.
And I heard, music bought digitally is giving more money to the artist, the label doesn't need to make some budget for printing the booklet and CD.
Well, just my random opinion (with awful English grammar too), so don't take it seriously.