My sense from past events is that he is not going to believe you. He thinks it is romantic, and there is nothing wrong with it being romantic either. Many times platonic love goes unspoken, agape is abstract etc. The vast majority of the time adults say ILY to people not in their families is romantic.

Obviously not always. . . but your T seems to have been on this wavelength before.

What do you think will happen if you tell your T that you love them?