The HD is really poor 3mbps HD for a prized event like Wimbledon, the world feed at 7e is 13mbps!
Others will have more experience, but 13mbps sounds on the low side for a world feed, one that will end up being compressed at least once more before it reaches viewers.
A fairly standard rule of thumb is that for the UK broadcasters, a 18MHz satellite slot is booked for the main feed.
That should give you (with normal modulation parameters) around 31Mb/s.
A backup at a cheaper 9MHz slot will give you 15.5Mb/s, and it sounds like this is what is being used here.
If you add audios to that (plus other data) then you can drop to 13Mb/s - just Dolby audio will take 2Mb/s.
When Dolby atmos is added to a UHD feed, then you end up booking a 27MHz slot to keep the vision acceptable.
I'd agree for a world feed that 9MHz sounds a little thin for HD - you can usually buy ad hoc slots of 4.5, 9, 12 or 18MHz quite easily from the usual leaseholders.