Can the battery of an iPad Pro be replaced?

I’m speaking from experience. Wanted to change my ipad pro battery because its been draining like crazy. It says on the website that they can replace your battery (for free under warranty or for a fee US$99 if not under warranty), but it is actually subjected to their diagnostic test. Your battery must fail certain diagnostic tests set by them. Otherwise they won’t ‘replace’ it for you. I learnt that they don’t actually replace the battery but they will give you a refurbished unit in exchange.

After using my ipad for 3-4 years, my battery is draining very fast and I wanted to pay to replace it. I brought it to the Apple Store, and they ran a diagnostic test. Despite my battery draining like 5% within 5 minutes in front of them, they said that the test shows that my batter capacity is like 92% and so its healthy and they cannot replace it, even if I want to pay for it. I find their results highly suspicious, they insist that my battery is in very good condition despite 3-4 years of usage and it draining very fast right in front of their eyes. They wanted me to disable several things and asked me to wipe my whole ipad and reinstall everything from scratch (without using the backup to restore). And only if the battery still drains then they will consider it again. I was unwilling to set up my ipad from scratch given that I’ve been using this for so long and have many settings and documents in it, so in the end, I just left it as that. I really wonder if any ipads would actually ‘fail’ their diagnostic tests

Yes! See https://support.apple.com/ipad/repair/battery-power for more information.

Keep in mind that, if you are expecting the battery to be replaced under warranty, Apple will run diagnostics to determine if the cause of your issue is actually the battery before agreeing to replace it.