I have check the ARM64 VM architecture, seems no size support Nested Virtualization which have the suffix of pdf, pls, or plds, etc

D2pds_v5 | Ampere Altra [Arm64] | Nested Virtualization: Not supported
D2pds_v6 | Azure Cobalt 100 [Arm64] | Nested Virtualization: Not supported
D2pls_v5 | Ampere Altra [Arm64] | Nested Virtualization: Not supported
D2pls_v6 | Azure Cobalt 100 [Arm64] | Nested Virtualization: Not supported
D2ps_v5 | Ampere Altra [Arm64] | Nested Virtualization: Not supported
D2ps_v6 | Azure Cobalt 100 [Arm64] | Nested Virtualization: Not supported
D2plds_v5 | Ampere Altra [Arm64] | Nested Virtualization: Not supported
D2plds_v6 | Azure Cobalt 100 [Arm64] | Nested Virtualization: Not supported

You can check details from this links

Further more, someone also confirm it, links