To be fair, Coffee Lake is presumably faster/better and not more vulnerable than other chips [0]. If you have to mitigate anyway, and you're desperate to get back to pre-mitigation performance parity, releasing a faster chip that still requires mitigation could be a reasonable option.

[0] Caveat: Skylake and later are extra-vulnerable to Spectre because they have even more aggressive speculative execution, but fortunately, the IBRS microcode update is roughly equally performant as retpoline on Skylake+ only.