Hi Stephanie,
I think keypeg has found the video,
and here is a pdf of the op.11-preludes, which seems to be the score of the video, too:
https://petrucci.mus.auth.gr/imglnks/usimg/f/f8/IMSLP75864-PMLP09363-Scriabin_Ausgewaehlte_Klavierwerke_Band_2_Peters_Op_11_filter.pdfwhere the prelude can be found on page 22.
The groups of three notes in the right hand are called "triplets", not "thirds".

(The first one is a "triplet", too, but with a pause for the first note of the triplet.)
I think in the pdf-score we can read well when each note has to be played, and which notes are SUPPOSED to be played together and which ones not. In the case of
this prelude it should be, thus, clear. But sometimes, it isn't so clear:
( Additional info now following ) :
In romantic or late / postromantic pieces, composers sometimes use notation which is simplified, and which mathematically SEEMINGLY doesn't "fit". (There are examples I know, which led, on other places, to MASSIVE discussions, e.g. in a Mendelssohn-Song without words, where SEEMINGLY "illogical" notation of triplets occur, there were triplets, of which, e.g., one note was SIMULTANEOUSLY a note of the triplet AND another note of "normal" value, and the "mathematicians" were very angry, because they couldn't understand this kind of "loose" notation.

I could give the example here, but I won't, because it's difficult to discuss.
Other examples with "loose" notation we find, e.g. often in Chopin's works, or in Debussy. Or Rachmaninow.
In playing, pianists who are mentally ok and can think, won't, for example, in works of the above mentioned composers, exactly calculate, WHERE ( or: "between which notes" of a "29plet",

) some single tone in the left hand is played: They play with feeling, and in such more complex structures you will notice that many pianists differ. For example,
at the end of the "Minute-Waltz" D flat major, op. 64,1, of Chopin, there is a fast right hand run, and single Chords during it in the left hand:
https://imslp.nl/imglnks/usimg/d/d7/IMSLP114892-PMLP02373-FChopin_Waltzes__Op.64_BH9.pdfNO pianist who is mentally ok will exactly calculate WHEN the left hand chords EXACTLY have to be played. This is fact, and is proved by many recordings of pianists, each of whom play it the way they want, or the way it comes close to the notation.
There ARE mathematical ways to exactly specify WHEN the notes should be played. But music is feeling, and only sometimes "maths", I think.

Cordially, 8_octaves!