The 7.5.1 is a patch release that includes a couple fixes to TypeScript declarations published with the package. See the 7.5.0 release notes for a complete list of changes since the previous release.

• Fix OGCVectorTile source types (by @MoonE in https://github.com/openlayers/openlayers/pull/15015)
• Fix return type of Layer#renderFrame (by @MoonE in https://github.com/openlayers/openlayers/pull/15005)