Another reason why it is helpful to include the phone model in the thread title is to help people know what it is when they are using Tapatalk. If I browse Tapatalk, which I have set to view unread threads, I don't know which forum the thread is in when I'm just scrolling through the list of threads I haven't read. If the phone model is listed, it makes it easier for me to reply with a helpful answer if the question relates to a particular phone model with which I'm familiar (for instance, I can help more with the Lumia models, since I've used them; but I'm not familiar with the Samsung models, since I've never used them).
With the phone model listed, I'm able to easily find threads I can help with and respond to those, while skimming past topics I already know I cannot help with.