Fix a legacy issue with older ts versions

[RaananW]

type in an import is 100% correct, but fails if used with an older version of typescript.

The thinEngine change is just for consistency.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

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