MS Excel / VBA help thread

I know this isn't the right thread but I don't think we have a generic "I work in Analytics" thread and this probably has the highest crossover.

If anybody works in Marketing Analytics, I'm kind of stuck a bit on some work. iOS15 brought in some changes which means Open Rates are affected and the prediction is that Open Rates would go up because "if one person on iOS15 opens the email then everybody who received the email on an iOS15 device will be registered as opening the email". This is what I've read online from multiple sources, I don't really have anyone more experienced or superior to bounce this off.

Part of the problem in confirming this is that when you send an email, you don't know which device or OS it's been sent to, only when they open it. So you can't isolate iOS15 sends and then see which % opened. The only way I know to really examine this is to layer OS ratio over Open Rate, so see how the breakdown of all the OSs has changed since the September release date.

Following the above theory, I should be seeing a big spike in the ratio of opens from iOS15 users, but I'm not. I'm seeing a small increase from when it was released, but I'm actually seeing a big increase in non-iOS and non-Android opens which suggests to me that actually iOS15 is obfuscating the data it sends back to the sender's email tool.

The client basically thinks we're (because obviously we're the only agency saying this??) bullshitting and the meteoric rise in Open Rates is because actually their email engagement improvements are working, I was hoping to make things clearer, but I really can't because I can't make sense of what I'm seeing.

Has anyone got any experience in analysing wtf is going on?