Interesting point cc if only because a DVT is not just a nuisance - it can be fatal. However I am not aware of any evidence that sitting in the office as opposed to further back causes DVTs. BA looked into this some years ago and couldnt identify a risk for pilots as opposed to passengers.
The reason is obscure, at least to me, but I wouldnt worry too much about it. More patients are being put on the newer oral anticoagulants that dont need monitoring with blood tests in any case - has anyone any experience of the CAA's position on returning to flying while still taking them?