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Any issue with IPv6 address mask >64 bits?

Reading 'RFC3513: Internet Protocol Version 6 (IPv6) Addressing Architecture' I see:

2.5.4 Global Unicast Addresses

All global unicast addresses other than those that start with binary 000 have a 64-bit interface ID field (i.e., n + m = 64), formatted as described in section 2.5.1. Global unicast addresses that start with binary 000 have no such constraint on the size or structure of the interface ID field.

Any mask > 64 bits would encroach into the "interface ID" field of the address. Does anyone know if this bit-boundary is significant? Will this bit-boundary be [is it now] 'enforced' somehow?

From the same RFC:

The space allocated for Global Unicast has a binary prefix of 001.

The RFC seems to imply that all IPv6 global unicast addresses have an interface ID field of 64 bits and therefore have a netmask of 64bits, or less, although this is not specifically stated.

For example, should a point-to-point link have a /64 instead of an IPv4-analogous /126?

Thanks in advance.

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