All I looked at was the resource format, so let's look closer.
1. Script numbering-wise, no script goes over #999, and none have SCI2-style names, compared to GK1.
2. Selectors start with Y, X, view, loop, and cel. In GK1 that's plane, Y, X, Z, scaleX, scaleY.
Gabriel Knight 1 is in all respects but the resource map format an SCI2 game. This EcoQuest is an SCI11 game in all respects but the version number.