Just like saying, test the service with $50, if $50 works without issues, $50k will also work without issues.
Crazy for them to think we'd believe that. Gullible people may fall for it, but someone who is in this forum should know better than to think because a service fulfiled a swap of a small amount means that would do so when you deposit a larger amount.
There are a lot of sketchy details about this particular service and until they are address, nobody ought to use them for any amount. However, i always recommend that whenever you are depositing a large amount in any custodial service, it is safer to do so in batches, rather than in one lump sum, just to be safe and sure.