I just noticed that the CKeditor spell check plugins are missing in the latest 6.2 build. I'm guessing that happened with the upgrade to CKeditor 4.0 (
LPS-30346) since the timing seems about right. They were still there in M3 but missing in M4+. They're still referenced in ckconfig.jsp - SpellChecker and Scayt - but it looks like CKeditor may no longer be automatically bundling those plugins.