The XTF_xxxx_CTRL flags, as their names hopefully suggest, affect the behavior or need for the combination of the Ctrl key with the xxxx (Home or End) key. When set, and assuming that the corresponding XTF_HOME and/or XTF_END flags are also set, then these bits reverse the behavior of the Ctrl key in conjunction with the Home and End keys. Thus, Home and End without the Ctrl key will be interpreted as exit keys, while Ctrl+Home and Ctrl+End will be interpreted as navigation keys (to jump to the first/last row).
Historical note: prior to 5.1.1133, Home and End navigated to the first/last row of the tree, unless you used the Ctrl key with them (and the XTF_HOME and/or XTF_END flags were set), in which case they acted as exit keys. Between 1133 and 1146, they acted as exit keys even without the Ctrl key. Then starting with 1146, the original behavior was restored (and the XTF2_xxxx_CTRL flags were introduced to allow you to choose between the two behaviors).
