A Contractor should act competently and promptly to a compensation event (written) and also mitigate the effects practically (unwritten). If it is practically easy to get additional resources and work in parallel with other works then they should, rather than just saying they will do it at the end with their own labour.
A subtle point as well. In your question you actually mean it is possible to carry out the works without affecting "planned Completion" as that is what you are testing. If a compensation event affects "planned Completion" then you get to move Completion Date by the same amount.
A subtle point as well. In your question you actually mean it is possible to carry out the works without affecting "planned Completion" as that is what you are testing. If a compensation event affects "planned Completion" then you get to move Completion Date by the same amount.