The changes are based on the Bulgarian and Romanian cadastre. The border is altered solely for islands where it is clearly established which country they belong to.

Discussed in Romania's Telegram chat: https://t.me/OSMRomania/19416

The changes are as follow:
https://www.openstreetmap.org/way/88358684 => RO
https://www.openstreetmap.org/way/85406121 => BG
https://www.openstreetmap.org/way/16889604 => RO
https://www.openstreetmap.org/way/213919011 => RO
https://www.openstreetmap.org/way/213918957 and https://www.openstreetmap.org/way/213919044 => RO
https://www.openstreetmap.org/way/17019070 and https://www.openstreetmap.org/way/17019111 => BG
https://www.openstreetmap.org/way/17503983 => RO