no, do not mistake yourself. they are not proprietary blobs. the whole browser is proprietary. they release a tarball with the chromium code + some changes. but the whole UI which are the main changes are proprietary (after all, like any Chromium browser, it’s mostly a re-skinned Chromium, they don’t make any changes to the engine).
It’s a proprietary browser. They just release a bunch of code for marketing purposes. Don’t believe me? Try compiling it, and tell me if what you get is Vivaldi minus some blobs.