This is because of a change Apple made in iOS 11 for truncating for longer app names. If the name is longer than 12 characters, the spaces will be removed. Otherwise, they'll still exist.
For example, Guide book app
will become Guidebookapp
, but Gui boo app
will stay as Gui boo app
.
Using unicode  
(FIGURE SPACE) works because it isn't an ascii space. I would be hesitant to use this as a solution because it seems reasonable that Apple would "fix" this bug and remove  
for apps with names longer than 12 characters.
https://forums.developer.apple.com/thread/77832
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