alright so Spiritmend = Spiritbeast?.
Pretty much,
by definition.
Note the details bar, which shows their abilities [or lack of] and whether the pet family is an Exotic (BM only) family or not, which is one of (if not the
main) details that distinguish
one pet from another, or more precisely one pet family from another pet family. Pet families are also precisely what distinguishes this
new fox (a
spirit beast) from the
fox family.
As for the example you shared earlier with the
Ghost Saber, note that even wowhead has identified it as part of the
cat family [tameable (Cat), under Quick Facts], and there's a difference between a
cat family and a
spirit beast family (and thus the relevance of this thread).
As for stuff like the
boost-mastery spell from spirit beasts, pet abilities were removed or changed between patches and expansions, like
Moths used to (until WoD patch 6.0.2) have a
10-sec-CD interrupt with a 4 second lockout (Serenity Dust) that was usable by all hunter specs, and since 6.0.2 that interrupt ability was replaced with a
battle rez (dust of life) (and dust of life is an exotic ability, meaning
only BM hunters can use it). Or
wolves used to provide a
+5% crit buff to the whole party/raid, and that was removed in Legion (with no replacement for wolves), among many other examples.
Hopefully that helped clarified some things. If there's any other questions, feel free to ask.