I agree that the rewards outweight the risks here - if enough folks can make their way to France I can see the Russian army in Ukraine taking a serious hit due to a lack of manpower - but ideally France and allies would be able to vet well enough to catch all the spies, and only block the spies.
I think there may also be a fear that Russian spies try to sneak in via this route as well, ‘false defectors’.
In particular it sticks out that Vadim Krasikov got into Germany via a French visa as per https://www.reuters.com/world/europe/vadim-krasikov-russian-hitman-sprung-german-jail-prisoner-swap-2024-08-01/
I agree that the rewards outweight the risks here - if enough folks can make their way to France I can see the Russian army in Ukraine taking a serious hit due to a lack of manpower - but ideally France and allies would be able to vet well enough to catch all the spies, and only block the spies.