Follow 247tabletennis on IG. A very credible source.
A pro after a major competition can easily go to their sponsor, teammate, coach, training facility inventory, etc pick out a new blade to try, train for 6-8 hours with it. Repeat the next day with another one.
If they happen to like one, dip the handle in hot water, slide out the handle and replace with whatever else they require for sponsorship reason. Heck maybe they can get someone else/their sponsor to do it for them while they’re testing another model.
Other examples:
Jeong Youngsik - Viscaria with Xiom Ice Cream handle
Jurgen Persson - Stiga Clipper Wood with Donic handle
Samsonov may have used Clipper and Mazunov with Tibhar handles in early to mid stage of his career.
Example more to market their own blade within Butterfly:
Werner Schalger - Primorac Carbon with Schlager Carbon handle
Kreanga - Primorac Carbon with Bty handle
Oh Sang Eun - Korbel with Oh Sang Eun handle
At certain parts Zhang Yining and Wang Liqin were using Korbel with their sponsor handle.
I’m sure there have been a lot more.