I know you can't make the Fiery Hellhound puns that way, but otherwise it means three people at Nationals messed up with that card. I can't imagine the tongue-lashing someone in the current Designer Search would get if they ever suggested a similar card to it.

It's 100% okay to tap your lands and put mana in your mana pool before you cast your spells. The rules just give you an opportunity when casting your spells to do so as well, in case you didn't before hand. There are also some crazy situations where it matters if you tap land for mana before you pay costs. (gemstone mine with one counter, tapped for mana to cast a spell that requires you to sac a land as a cost, you can't sac the gemstone mine because it already sacrificed from its own mana ability before the rules ask you to sac it for the spell)

Bottom line, the way your doing it is okay.

Did I get taught wrong? (FYI, I learned around the time of VIth Edition.) I thought you had to have mana in your mana pool before playing a spell?

As much as a card might be clear to you, or me, or even most people, if a player doesn't agree with the judge's ruling, he can always appeal to the Head Judge. Sometimes there isn't one (most FNMs or other store level events, it's just whoever is running the event), but if one exists, they are the final authority on all judge calls. If we denied players a right to appeal because the call is simple, they might think they will get denied when the floor judge does make a mistake.

A player can always appeal a ruling