Would Tsushima happen without the Russian signal?

Would Tsushima still have happened without the Russian signal to a ship thought to be a noncombatant?

Yes, because the Japanese were already prepared for the Russian fleet.

Removing the Russian signal to a vessel thought to be a noncombatant would still leave Japan ready for the approaching fleet. Tsushima is therefore expected to happen even without that signal. No alternative detection or interception sequence is specified.