They're comparable in a couple roles, but for the most part Timburr outclasses Croagunk in those roles. If Croagunk were to be A, then it's not because has a meta defining role or some unique, essential niche, but because it's able to fulfill more than one role at once. The problem that keeps it B in my opinion is that it's being thrust in a defensive role by those arguing for A without recovery. That is where the forcing switches as an argument against it comes into play- Croagunk can't continue to do its job when it's worn down, and doesn't have good enough bulk to overcome that.
As for the fact that it beats Timburr, it better be able to beat Timburr, or else I'd be arguing that it'd go down to C rank. One of the main things that's been argued in its favor is that it counters the common fighting types in the tier. If it couldn't beat one of the three it has to, then it doesn't deserve A rank in any way. However, the argument that it counters fairies is very, very weak. Croagunk obviously beats or forces out Cottonee (but would you leave something like pawniard in on a fighting type?), but Snubbull beats it with Earthquake, and Spritzee...
12 SpA Spritzee Moonblast vs. 212 HP / 116 SpD Eviolite Croagunk: 7-10 (29.1 - 41.6%) -- 99% chance to 3HKO
108+ SpA Croagunk Sludge Bomb vs. 212 HP / 76 SpD Eviolite Spritzee: 14-20 (51.8 - 74%) -- guaranteed 2HKO
Quiet, 0 Speed Croagunk speed ties with 12 Speed Spritzee, bringing it down to a 50/50 chance. But making it even worse for croagunk is the 30% chance of a special attack drop from moonblast. If Spritzee wins the second speed tie, or Croagunk gets a special attack drop when it switches in, Spritzee will win. That's not good for Croagunk's ability to counter fairies, as now it's at 1 absolute counter, 1 kinda sorta counter (less than 50% of the time) and one kinda sorta check (Croagunk speed ties with min speed Snubbull too).
Timburr outclasses it in terms of pure power but not versatility which was my point....again. You say "without recovery" but it has more reliable recovery than Timburr does in Water Absorb so that point really works against you. It further brings up the fact that unlike Timburr and Mienfoo, Croagunk does not need full HP to do its job against Carvanha and Tirtouga since they can't do anything with their water-type STAB and need to use their other STAB that's resisted and has no flinch chance.
I never said that mix gunk counters Spritzee but the other sets all do. Additionally, even just checking Spritzee is something the other Fighting-types can't do in the first place. Comparing Croagunk to a weak Timburr just shows a gross lack of experience with it, frankly.
Snover is B because it can either do Blizzspam, which is still a hard attack to switch into if you lack a resist, or it can run DEFENSIVE SNOVER. It might move to C though, considering there's no more Murkrow for it to Blizzspam beat. It does surprise Fletchling with ice shard, though.
0 Atk Snover Ice Shard vs. 156 HP / 92 Def Fletchling: 12-14 (52.1 - 60.8%) -- guaranteed 2HKO after hail damage
(12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 14)
196+ Atk Fletchling Acrobatics (110 BP) vs. 0 HP / 0- Def Snover: 38-48 (172.7 - 218.1%) -- guaranteed OHKO
(38, 38, 38, 42, 42, 42, 42, 42, 42, 44, 44, 44, 44, 44, 44, 48)
Surprise!