The former release date of 1997-12-28 is from BANDiT and the website has usually been pretty accurate for documenting this kind of music. Notably the entry for this CD does not say anything about it being an enclosure / first press item. 販, if I interpret it correctly, indicates the CD could have been obtained by some sort of sale/trade. The date given is the first day of Winter Comiket 1997.
Another part of the archived Apricot website seems to confirm this was not a first press bonus but rather produced for event sale, and sold at Comiket for a price of 1,500 Yen
http://web.archive.org/web/200006031.../ap_kanren.htm
夢幻夜想曲音楽ＣＤ 製作：アプリコット ￥１５００
コミックマーケット企業ブースでの販売用に製作されたものです。