Using stockvideo for a splashscreen on my app

Videos come only under an enhanced licence.

This is, what Adobe says of an enhanced licence:

Enhanced licenses

Enhanced licenses are available for Adobe Stock videos, templates, 3D assets, and Premium Collection.

With an Enhanced license, you may:

Use the asset with all the rights granted in the Standard license.
Reproduce the asset beyond the 500,000 copy/viewer restriction.

With an Enhanced license, you may not:

Distribute the stand-alone file.
Create merchandise, templates, or other products for resale or distribution where the primary value of the product is associated with the asset itself. For example, you can't use the asset to create a poster, t-shirt, or coffee mug that someone would buy specifically because of the asset printed on it.

As you do not distribute the standalone file (!) and the video is not the primary value of your product (!). I suppose that your use is OK.

Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).

If you believe that your app will be viewed less than 500,000 times, I think the standard license is sufficient.

With a Standard license, you may:

• Reproduce up to 500,000 copies of the asset in all media, including product packaging, printed marketing materials, digital documents, or software.
• Include the asset in email marketing, mobile advertising, or a broadcast or digital program if the expected number of viewers is fewer than 500,000.
• Post the asset to a website or social media site with no limitation on views.
• Include the asset in some types of products, such as inside a textbook, as long as the primary value of the product is not the asset itself, and the product is not reproduced more than 500,000 times.
• Share the unmodified asset with your employees and contractors who have contractually agreed to abide by the license terms.
• Transfer the license to your client or employer.