I will answer your question and also point out that you may have slightly confused other float terms within the same question.
Firstly, float prior to a Key Date IS as per the terminal float associated with Completion Date which is clarified in the second sentence of clause 63.3. The second sentence repeats the first sentence but replaces the words “Completion Date” with “Key Date” emphasising that it is the same rule, i.e. Contractor owns terminal float associated with Key Dates as well. Any such terminal float is owned by the Contractor and retained in the assessment of any compensation events.
Secondly it is better to use the term “total float” rather than “free float”, free float being part of total float and either Party can use total float when assessing change/compensation events. Time risk allowances are risk the Contractor has allowed against their own activities for risk which are theirs ad their for owned by the Contractor.