Yes they do. I uploaded them directly.
So to summarize:
LR Classic does not sync videos to LRCC (cloud).
Videos can be directly uploaded into LRCC.
From there they are downsynced to LRClassic to where the LRCC ecosystem's folder is set.
And so they appear in LR Classic within the collection "from LR Mobil" (or similar) together with a Sync sign. This sign is pointed to the name of Album in LRCC which becomes a collection in LRCL. The parent folder is not synced, hence a video that resides in the Album "Winter" within the Folder "2017" in CC is just seen as residing in "Winter" in LRCL.
This video can be edited in LRCL, but changes are not synced. Videos can not be edited in LRCC at all.
So uploading a14Gbyte video also creates a downsync traffic of 14Gbyte.
(LRCL's Slideshow MP4s are huge, like 10-14 GByte (1080P) for 600 slides. They consume the LRCC cloud space easily. Recompressing them in PPro's two pass MP4 encoder cuts size to 1/3 with little loss.)