It wasn't an SPL or SFA issue. The difference between the Juninho EBT and the ones mainly discussed in the Rangers context was that the Juninho payment was after his contract was terminated, as severance pay, and not while he was a registered player.
The problem with Juninho was they hadn't declared it to SPL/SFA so had to settle issue.
And Celtic also payed the tax on that EBT when they realised it was a potential problem.
Celtic did it with one player whereas with Rangers it was the owner down to the clean, dozens of people and untold millions.