So, presumably the source of this advice is the fact that tourneys with players who little or no financial investment, play quite differently when compared to cash or cash-entry tourneys.
But that isn't to say there is no value in learning poker there. Poker is not "one single thing" to learn, but a complex array of information, skills, experience, probability, maths, notes, etc. etc.
So -- at the end of the day, where do you plan to play? If you play freerolls, it is a good idea that you spend some time there.
The difficulty is translating that strategy to non-Freeroll games.
As many will have already noted, freerolls differ in a few main areas:
1. BINGO: The field is littered with bingo players.
2. STARTING RANGES: Even non-bingo players tend to have a much wider range of starting hands.
3. CALLING RANGES: Calling ranges are also much wider in freerolls
4. BLUFFING: Point 3 leads to the virtual impossibility (at least in early game) to bluff freeroll opponents off the pot.
5. POSITION: Since you are going to witness far more multiway pots in freerolls, you really need to pick your hands and your position. Shoving AA/KK/AKs from early position is going to get cracked a significant portion of the time if 4+ people call you. So generally, you're going to need to shy away from early position shoves, and you'll need to leave options to fold post-flop, if you manage to flop poorly.
BE A SHARK: In freerolls, at least in early/mid game, you want to feed like a shark. You are nowhere to be found until "CHOMP!" you re-raise/shove your KK/AA/AKs and stack your opponent(s). You then retreat to the depths leaving people nervous that you could strike at any time, (but only do so with very sharp teeth).
As you go up the stakes, the Bingo players thin out considerably. They still exist. And there are of course, people who are going through a cycle of tilt, who can become a bit wild (especially after losing a big hand).
Starting ranges get narrower. But you should be playing tight, exploitative play in both situations...But generally, if you're new to poker, what you think is tight is not tight enough.
Calling ranges also narrow as you go up the stakes, but there is still variability. The thing here is that you need to generate intel on your opponents. You need to understand which plyer at the table is the fish with the wider range. You need to take this into account when you play...just as you do in the freeroll..
The good news is, the bluff can be let out of your bag of tricks as you move up. The best people to bluff against are those with the narrowest calling ranges. The tighter they are, the more you can exploit.
Although early play is not as desperate as you move up the stakes as freerolls, position really is the key to winning. If you review the hand history of a successful player, you will note that most of the chips are coming from BTN, CO and HJ positions. This is because they've avoided butting up against the NITS betting from early position, whilst exploiting late position by putting significant pressure on downstream players.
So -- you CAN learn that way...as long as you recognise the differences between those games and others with folks who are literally more invested.
Also note that not all freerolls are created equal.
For example, Cards Chat League does not seem to suffer from the "any two cards" philosophy which you see early-game in freerolls. This is a very competitive league where prestige and recognition are important...and your results in one season influences the draft in later seasons. This kind of freeroll gives a great view into how some really good poker players operate.
But in all situations, I like the be a shark philosophy... but you need to be prepared to adapt. If you play like a NIT and everyone knows you are, you'll quickly find that people just fold when you're opening a pot and all you get are blinds. When this happens, you can adjust and steal a few extra pots (until they realise you've loosened up). Find the sweet spot where you leave them uncertain enough to get caught out calling (or leading into) your monsters.
Happy chomping!
Cheers,
ObbleeXY