That is certainly inconsistent, but TOS had a knack for messing with Warp speeds... at one point, the fastest the 1701 could go was about 1000 Ly's per day if I'm not mistaken. The Magellanic clouds are 160 000 Ly's away. At the speeds from TOS, you can get there in about 6 months.
But then you're presented with another conundrum: 'if those warp speeds did exist back in the day, why weren't they ever used by the rest of the fleet'?
And by the time of ST:V, the Enterprise supposedly went from Earth to the center of the galaxy in just a few days, implying that SF increased those Warp speeds from 1000 Ly's per day, to about 10 000 LY's per day (which definitely seems plausible increase for the passage of time and technological advancement - but in-universe wise, it makes 0 sense because the rest of the fleet never used those speeds - and VOY by that analogy would have returned home in a week without any technological advancements taking place in the interim - that's why I suggested it would have made more sense for VOY to be thrown 273,750,000 Ly's from its last known location (aka, hundreds of millions of ly's) make it back home in 75 years at a speed of 10 000 Ly's per day.
In the same vein, let's talk about running from Daystrom Station to Athan Prime, having a less-than-alacritous disagreement, & then heading back in less than an hour's time—with both places implied to be in different star systems. YEAH OKAY.