Please stop perpetuating this incorrect understanding of the rules. The marker must be placed on the LOP which does exist.
Relevant rules
So at this point in time, the thrown disc is the marker disc and has established the LOP. When marking the lie under 806.06.B, the LOP has already been established by and does not change when marking with a mini marker disc.
Incorrect.
802.05.D defines the LOP as:
The line of play is the imaginary line on the playing surface extending from the center of the target through and beyond the center of the marker disc.
Since the LOP is defined with reference to the center of the MARKER DISC, rather than the center of the thrown disc, the LOP only exists after the thrower has marked the lie.
By allowing the disc to be marked with a mini rather than requiring ONLY the thrown disc to be the marker, but NOT requiring that the mini to be centered on the LOP established by the thrown disc, but only that it be ON the LOP that would be established by the thrown disc if the thrown disc is used to mark the lie. Consequently, ANY placement that has any part of the mini touching the potential LOP of the thrown disc is permissible. Given that mini marker discs must be between 7-15 cm in diameter and the maximum diameter of an PDGA approved disc is 30 cm, a 15 cm mini may be placed with its center up to 7.5 cm left or right of the LOP of the thrown disc and still conform to 806.02, provided it also touches the front of the thrown disc. You can argue that that's not the intent of 802.05.D, but you cannot argue that it is prohibited by 802.05.D as it is currently written.
Furthemore, the intent of a rule is not always, nor necessarily, determinative for interpretation and application--nor should it be: ask Dave Dunipace, who was on the RC at the time the original practice throw rule was written and further claimed who claimed to have been the one who wrote the original rule, and who protested on the old PDGA Disc_cussion board that application of the rule governing practice throws, no matter the distance, that were made to return a disc to a player, to set aside a disc, or to retrieve a disc above 2m, were was contrary to both his and the original RC's intent in promulgating the rule.
If you think any point(s) in the above interpretation should be disallowed, you're free to lobby the RC to amend the rule or issue a Q&A disallowing it (them), but until such time as the rule is amended, the interpretation and the application following from it remain valid.