Went to a Different Technician, Now My Z800 Runs Hotter – Advice Needed

Last week I had to visit a different service technician for my Kawasaki Z800 because my usual guy wasn’t available, and the chain rattling issue was driving me crazy. The new tech pointed out that my engine oil was low. He showed me the see-through glass on the right side, and I couldn’t see any oil either. I told him to go ahead and change the oil and filter. I’ve always used Motul 300V 10W-40, but this guy decided to do things his way. He put the bike on a paddock, measured 125ml of Motul engine oil flush, ran the engine for 5 minutes, and then drained the oil. To my surprise, the drained oil was less than 2.8L. He then replaced it with Motul 300V 15W-50 (3.4L measured) without consulting me. When I questioned him, he insisted it wouldn’t make a difference, citing our local temps (16-28°C). Now, the bike is running hotter than usual. Previously, it stayed at 95-101°C, but now it’s between 98-103°C, with the radiator kicking in after 100. Should I switch back to 10W-40, or is 15W-50 fine for the Z800 (38k+ kms on the ODO)? Any advice is appreciated! Picture just for traction 👾