Any Updates On IOS 12 battery health after battery replacement?

There are a couple of older threads here about iOS 11.3 beta where battery health shows “service” after replacing the Apple battery with the iFixit battery. I did that replacement with iFixit batteries to two iPhones 6 and a 6+ about 11 months ago and had no issues. Performance was clearly improved in all benchmarks (using GeekBench 4) after replacement suggesting the iOS throttling was deactivated. After upgrading to iOS 12 and 12.1 the battery utility still cannot read the battery and shows “service”. While those same benchmarks after upgrade to iOS 12 show even greater CPU performance and do not hint at throttling, I am still concerned that iOS will start to throttle the device because it cannot read the now 9 month old iFixit batteries. That is because the Battery Health utility still shows “service”. Other forums are unclear. Does anyone have any specific knowledge or experience to offer? When I replace the battery again next year, should I buy from iFixit or try to get from Apple, if that is now possible?