The Spurs have an an absurdly young team for their standards for like three or four years now. It's funny that people would think that means tanking when teams that were unabashedly tanking like Process Sixers still had older players on their roster.
My guess as to why the Spurs are hanging around the talks is to take guys like THT and Harris to save the teams money on the backend for assets. Harris has value in the right situation, but that situation may not be apparent. Or they might have value to a third team with only bad salary and assets to give, which neither principle team wants but SA might stomach for compensation. Also, though Harris is basically McDermott but more expensive. He's negative value for LAL, but swapping him out for Doug or even Richardson might be enough to get them to give up something good to the Spurs. Good enough? I don't know but like:
Westbrook and the 2027 first to BRK
Irving, Richardson and McDermott to LAL
Harris, THT, the 2029 first and additional incentive (seconds and/or a swap in 2026 or 2028) to SA
Saves both LAL and BRK a good deal of money. Get the Spurs another unprotected pick and a double-swap to boost the value of either the 2026 or 2028 first. It would encourage the Spurs to focus on near-term returns for Poeltl and the rest of their cap space, as their future would be stacked with quality assets.