It’s a very nice theory, but Dumbledore’s (and the other characters’) reactions to Lucius proposing the deal don’t quite seem to match. Lucius also seems sincere about considering it a real blood debt from Dumbledore comparable to an attempt on his son, I don’t think he’s a high-level enough player to have even the narrator not mention anything suspicious about it if he were faking it.
It’s a very nice theory, but Dumbledore’s (and the other characters’) reactions to Lucius proposing the deal don’t quite seem to match. Lucius also seems sincere about considering it a real blood debt from Dumbledore comparable to an attempt on his son, I don’t think he’s a high-level enough player to have even the narrator not mention anything suspicious about it if he were faking it.