The rule for a blanket NTO vs. multiple NTOs is based off whether there is 1 contract between the GC and the owner of the project. If they do not know if there is 1 contract and there are multiple NOCs, then we would send multiple NTOs.
For multiple residential lots that have separate NOCs even though there is 1 contract (between GC and Owner), it would be best to send multiple NTOs as well, one NTO for each NOC/lot in case they start selling the lots as they get finished.
For example, there are 10 lots being built, there is one contract between the owner and the GC but each lot has its own NOC, if the owner/developer sells only lots 1 & 2, you shouldn't do one lien to reflect all the lots and all the owners. The best business practice is to do one lien for lot 1 with the old and new owner, one lien for lot 2 with the old and new owner and the other lien for the other lots that have not been sold and are still owned by the developer. As there were separate Notice to Owner forms for each lot, you may file such separate liens.
There are other facts to take into consideration, such as the NOCs being terminated when the lots are completed and so that they can be sold, regardless, if you are within the 30 days from the notice of termination you can still lien for that specific lot.
Another case, if you got paid for each lot separately, you may file separate liens only on the lots that you did not get paid for, because you secured your lien rights for each lot, by doing separate NTOs.