PhilipG,
I'd very much doubt there's any embarrassment, as much as the jet's detractors would like there to be. If you remember, the first trans-Atlantic move was planned for June 2014 but, due to a completely unforeseen and catastrophic engine problem, the Program wisely curtailed the trip until they could take adequate stock of the situation.
Roll forward a year and the USMC focus was their IOC. The Marines had offered huge support and help to the MoD to send the jets to the UK in 2014 but their more important IOC meant they couldn't in 2015.
Roll forward another year and the plan is to very much get the jets to the UK for this summer.
Of course it's very easy to look at the above facts in isolation and spin them into whatever narrative one chooses.