Actually, it was well-known long before MythBusters that tomato juice was only marginally effective.
The problem here is that the tomato juice thing is FAR more widely known than the MB debunking. Pretty much everyone and their grandmother would know what Pirta is talking about when he says "tomato juice", but few- if any- would know what she was referring to if she wondered how much hydrogen peroxide she had on hand.
Actually, as that's widely used for bleaching or lightening hair, quite a few readers might have thought she was somehow referring to a whole-body dye job.
And it was already a kind of iffy gag since Jake's only been seen a very few times in the last year or two, and some readers may not know or remember he's a skunk- plus the last "accidental discharge" gag has to be something like six or seven years ago.
So yes, it was better for the gag to stick with the much-more-widely-known wives'-tale for the gag, than an actual solution. Call it artistic license.