I don’t think there’s much difference. If you argue that companies like Stripe and Twitter should “uphold freedom of speech”, then you’re restricting their freedom of speech.

My right to speak doesn’t override you’re right to ignore me, or refuse to transmit my message.

Now there’s a knotty issue with entities like Facebook and Twitter becoming the primary ways people communicate with large audiences, but people managed before Facebook and Twitter, so they can manage again.

Or the alternative is that we say Facebook and Twitter don’t deserve to have their own speech protected. At which point someone is picking a choosing who deserves free speech.

You can’t have it both ways.