I do wonder if this is due to automated A/B testing, similar to how you can upload multiple thumbnails on YouTube, and the algorithm will automatically choose the one that provides the most traction.
If the sole purpose is to generate as many clicks as possible, that kinda tracks.
With normal news websites, A/B testing could be a thing. We had a rudimentary implementation of that back in 2011 already.
But this is Reuters, a news agency. They are B2B and don't care about clicks, their business model is selling first hand reporting to other media outlets (e.g. CNN, USA Today etc).
As stories develop, so does the title. Especially when ongoing conflicts are concerned.
I thought it used to be done manually, but now there's automation built in to YouTube, I recall hearing. It might only be available to certain users, though.
I think I recall it being discussed in relation to Veritasium, although I can't recall if it was a third party mentioning it or Derek (Veritasium) himself.