Honestly, sometimes I wonder if the tension is more in the reader's head than on the page. We're conditioned to look for romantic clues, so we read significance into every interaction. The 'slow burn' label primes us to be hyper-vigilant, to scan every line of dialogue for subtext. The actual narrative might just be building a deep friendship, but because we're waiting for the romance, we interpret all that foundation-laying as simmering tension. The 'burn' is our own impatience, our projection of desire onto the characters. The skill of the writer is in making that projection feel inevitable and earned, rather than a trick of reader expectation.