The explanation may be in the pronunciation. English is a language with very lazy pronunciation. Both words would be pronounced Schulenberg in English, in the same way that burger is pronounced berger and Gettysburg is pronounced Gettysberg. German is not widely taught in Britain so most would not differentiate between burg (bourg) as in town, and berg as in mountain. Most British people do not realise that iceberg means ice mountain.
Even written English is difficult in some parts of Britain owing to local pronunciation, e.g. in my home town of Liverpool most people pronounce where and were in exactly the same way (i.e. as where), which leads to frequent written spelling mistakes. In other areas of Britain where is pronounced as wear whereas were is pronounced as whirr.
The people at Pendraken have been at it again and have now added colour photos of their Hanoverians (in the wrong uniform - apparently they look like Hessians as they have been painted blue), French and miscellaneous items, including the personalities, civilians and general's coach.
The only problem with that approach is that if I did buy any Kallistra they would be very much in the minority and all the other troops would have to be put on thicker bases. Consequently Kallistra WWI don't get a look in.
Had a quick look at the Vikings, who appear to be nearer 12mm. This makes a difference, from company to company, e.g. with my WWI 10mm Belgians, Pendraken figures work well with Irregular 10mm and Van Dyck 12mm, but not with Kallistra 12mm, which are very much bigger.