You need to check the manufactures installation instructions for the make & model of oven..
The fact that it is not a pre-fitted moulded plug already fixed to the flex, suggests that the oven is NOT designed to be run off a 13A plug!
(Some single ovens are, but all the ones I have seen come with a plug already fitted..)
I also thought there was a legal requirement for UK appliances to come with a fitted plug if they are designed to be operated in a domestic environment via a standard 13A socket outlet? e.g.
https://www.hse.gov.uk/foi/internalops/ocs/400-499/oc489_6.htm
I do also know that some ovens come with a connecting flex. but are designed to be used with a hard-wired connection fused via a 16A MCB. Not a 13A plug top cartridge fuse!
Also IMHO.. Those ovens that are designed to be plugged in should NEVER be connected through a double socket outlet..
Just the same as it is not good having washing Machines & Tumble driers sharing double sockets with other appliances...
Basic rule:-
If your appliance is consuming a lot of power, (higher currents), for more than a few minutes, then it typically needs a dedicated single socket outlet for reliable continued long term usage.. NOT a double socket..
Most double sockets are not actually designed to supply 2x 13Amp loads..
I recall some manufactures suggesting 20Amps max shared between the two!
(e.g. 10A & 10A or 13A & 7A)
Kettles / Toasters / Coffee machines / Kitchenaid food mixers etc.. don't consumer power for long time durations, so they can happily share double sockets..
But Ovens are never a good design connected to a double socket.!!