I don't agree with this. I think even using a trade boost for corrections post round 2 if there are glaring errors in your starting side is beneficial. For example, if one didn't have Brodie start of this season and needed to correct a rookie and also get in someone like Hewett, using a boost to correct that would have yielded far more long term gains than being conservative and waiting to use one in the byes.
I think strategic use of trades has always been the key to SC, and the boosts just added to that.
Me personally, I used mine in the following rounds:
Rd 7: Unexpected Grundy injury, didn't want it to ruin my planned trades.
Rd 10: Steele injury, see above.
Rd 13: Bye tactics
Rd 14: Bye tactics
Am still holding one, 6 trades left and have moved into 98th spot overall.
Of course it depends on your squad. I got lucky with my starting picks/rookies and didn't have to chase too many. I would have advocated for early aggressive trades to correct rookies pre-round 3 for sure.
Will be interesting for everyone to do a trade analysis at the end, I'll bet many are regretting wasting (I'd guess) 5-10 trades for 'flavour of the months' or chasing last week's points.