For this let's take an example those two simultaneously released 『萬花鏡』＋『密航』 and 『胎児の夢』＋『蝶のすむ部屋』 compilations.

1. 『萬花鏡』＋『密航』 (CDSOL-0018/19) compiles 1st and 2nd album
2. 『胎児の夢』＋『蝶のすむ部屋』 (CDSOL-0020/21) compiles 3rd and 4th albums

 
Those are ordered correctly in their Solid RECORDS label page.
Where the current order (date / cat. / etc.) is enough for this.

But in the 佐井好子 (artist's release groups) and 佐井好子/releases artist pages, the order is not only inconsistent but not good.
Problem : 3rd/4th albums come before 1st/2nd.
I don't know the current sort order but it would be good to incorporate catalogue number (and bar code MBS-6975) as in label pages, in the same consistent order.