Over a month ago I bought some expired domains and it still says "Pending deletion or renewal" in the owner field althrough the expiry date is extended.
How long it takes to change the whois on expired domains?
Once the domain is moved into your Dynadot account, the original Registrant can no longer renew or restore the domain.
The original Registrant can only renew the domain in the 3-4 day period after the auction has ended but before it has been moved into the highest bidders account.
For domains bought through the auction, the Whois is updated 30 days after the domain is moved into your Dynadot account. This is also when the Auction Lock is turned off.
During the entire Post-Expiration period, the original registrant has the right to renew the Expired Domain, regardless of any payments You may make in an effort to purchase the Expired Domain. By bidding on the Expired Domain, Buyer acknowledges and agrees that if Buyer has the winning bid, the transfer of the Expired Domain will not be completed until after the Post-Expiration period lapses. If the Expired Domain is renewed by the original registrant, You will receive an account credit for the full purchase price, or, at Dynadot’s sole discretion, a refund.
However it is also worth noting that during this period (whilst it says Pending Renewal or Delete) it is still possible for the original Dynadot owner to renew the domain name.
If this happens you will lose control of it and it will be transferred back to the original owner. Dynadot will credit your account with the amount you paid.