Even if Master Golden Sword Zen Ren had not refused, Lin Yi would have declined the requests of those Golden Core Real Persons. His reason for giving free lectures to the disciples of the Golden Sword Lineage was to repay his gratitude towards his Master.
As for giving lectures to other Golden Core Lineages, he had no such intention. With his spare time, he might as well improve his cultivation level.
Master Golden Sword only stepped forward to refuse on his behalf to prevent him from being resented by the Golden Cores.
But with his current strength, the resentment of some Golden Core Real Persons was irrelevant now.
Even if someone leaked this information and attracted the attention of Nascent Soul True Monarchs of other sects, he had nothing to fear. He could continue lurking in the Liu Yun Sect.
In the eyes of others, he was still a Foundation Establishment Cultivator and would be looked down upon by others unconsciously. That was his biggest advantage.