Historically (especially on non-iPhone phones), fast chargers could cause battery issues. Bigger devices like laptops without great battery management strategies (read: Microsoft or Linux) also see battery health reduce 2-3x faster when charging to 100%.

But for phones/mobile devices - Nowadays it's mostly smaller devices like headphones that might be vulnerable.

I have still observed fast chargers causing issues: My USB-C bluetooth headphones died after 2 months (could only hold battery for 30 minutes rather than 8 hours).

I started using another pair and was refreshed by the full 8 hours, thinking the first pair was a random issue.

But soon they were also running out after 6-7 hours.

I switched to the charger they came from an voila, they have kept 6-7 hours for months. Frustrating, because now I have to charge them for at least an hour or two, rather than 10 minutes, but at least they'll keep the battery health now.