clients.  It listens for IPv6 router advertisement messages, for example
     those sent by rad(8), on interfaces with the AUTOCONF6 flag set.  slaacd

I'd flip the sentence around to state the dependent sitation first, and
avoid the vague word "it".

    For interfaces with the AUTOCONF6 flag set, slaacd(8) listens for IPv6
    router advertisement messages [...]

As to what either of these two daemons does with the information, that's
much more complicated.

    The interface may then be configured with an learned(?)
    dynamic(?) address, and DNS-related information is provided
    to resolvd(8) to handle.

And then use the same style of sentences in dhcpleased(8), they should
indeed be more similar.