That's how it originally worked, but with the proposed changes, turning blocking into effectively muting, a spammer can still see tweets from the spammed accoun

That's how it originally worked, but with the proposed changes, turning blocking into effectively muting, a spammer can still see tweets from the spammed account, but the spammed account will no longer see tweets from the spammer. Note: twitter has backtracked on this change anyway, so it's back to how it originally worked.