According to Zackray's (Perhaps outdated?) chart, Wolf actually loses to the Marcinas, and Shulk. And only goes even vs Chrom.
I do think Wolf is a very solid choice however. But I actually believe Inkling is the objectively best Mario Secondary. At least according to Cosmos + Wizzy's Matchup Chart.
https://pbs.twimg.com/media/D5m-54mXoAEvmUF.jpg
https://media.eventhubs.com/images/2019/03/28_cosmo01.png
Inkling beating most swordies, and Mario going even with Peach/Oli, and beating Rob works out super well.
There's also a good level of overlap with how bair-centric they are. (Though their mix-ups from bair differ quite a bit) As well as better stage coverage, as Inkling's Mobility and options make them better Picks in situations they're clearly trying to ledge trap you, and take away platforms which help you escape. (FD, SV, etc)
I also like that Inkling's biggest weakness is the lack of OOS options. Which Mario has in spades.
(Though I actually do believe Mario is solo-viable)
Edit:
Actually, after actually looking more into Inkling and the controls required of them; I don't think they're quite the ideal secondary anymore.
To properly ledge trap using Dair (Full hoping to feint a fair, then dairing standard/roll/hang and true comboing into uair) and getting the spike hitbox, you need tilt stick. Smash stick makes you fast fall. And this really hurts inkling's consistency at higher percents.
Wolf is still good, though they have a common enemy in Lucina.
I'm more leaning towards Palutena now. Boasting still better matchups against Lucina, and Snake. As well as performing overall better on Tiny Triplats like BF, Lylat, and Yoshi's melee.
Not as perfect* matchup coverage as Inkling, but is an overall easier character.
But man, Inkling really would be perfect if not for this issue.