A distributed port scan operates by:

Blocking access from scanning clients to the targeted host describes a firewall or access-control response, not the mechanics of how a distributed scan operates.

Using denial-of-service software against a TCP port range describes a DoS attack, not a port scanning technique.

Blocking access to the targeted host by the scanning clients is nonsensical in this context and describes no recognized scanning methodology.

In a distributed port scan, a coordinated group of machines each probe only a small subset of ports or hosts, then the results are aggregated centrally. Because each individual scanner sends very few packets to the target, threshold-based IDS rules and rate-limiting defenses are less likely to trigger on any one source, effectively evading detection while still gathering full scan data.