Seller won't hand over property vacant, Red Flags?

[Ryan Pearson]

I just went under contract on a row home property in Philadelphia. It's a 3 bedroom 1 bath SFH with current tenants paying on a month to month lease. Seller is requesting cash offers only and 30 days or sooner on closing. In the original offer we requested for the seller to provide the property vacant at closing. The listing agent got back to us saying "serving vacant would be a deal breaker". Owner has verbally said to our agent that the current tenants are up to date on rent. I'm assuming the seller is apprehensive that serving vacant could delay closing? Other than that I don't understand why the seller would not want to provide vacant at closing. I even requested permission and reached out to the current tenant to get more details but have not received a response. Does this give off any red flags to anyone? Does anyone have any advice on what we can do to protect ourselves in this situation? My biggest concern is that we get the property and the tenants refuse to leave after terminating their rental agreement. I appreciate any advice.