Yeah exactly. It's a nuance thing. Hard to give a one size fits all for this. But by saying "I have some time open on X" you force the other person to say "that

Yeah exactly. It's a nuance thing. Hard to give a one size fits all for this. But by saying "I have some time open on X" you force the other person to say "that's no good how about y" at which point, assuming your schedule is open, you can say "sure" or simply ask the person what other time is good for them (avoiding sounding like anytime is good for you).