Just last week, I highlighted the tectonic shift taking place in the global bond market in arguing that markets may have to get used to an era of structurally higher yields. And yesterday's announcement from the US Treasury offers another interesting test of that argument.The Treasury said that it will buy back as much as $6 billion of 10-to-20-year government bonds, tripling the previous $2 billion size.Now on the surface, that should be supportive for bonds. The theory is that Treasury buying removes older securities from the market, helping with liquidity while creating demand and pushing down yields.But instead, we're continuing to see 10-year Treasury yields hold near 4.85%, its highest since 2023. So, what gives?Why didn't the Treasury's $6 billion buyback push yields lower?It is a simple case of expectations versus reality, a tale as old as time in markets.The problem here is that markets were already expecting Treasury to step things up.Bessent had said last month that they would increase long-end liquidity-support buybacks from $2 billion to at least $4 billion. So while $6 billion is definitely larger than what was signalled, traders had been looking for something closer to $8-10 billion based on his communication and fighting words after.Plus, there wasn't much of any clearer commitment to substantially larger interventions moving forward in the latest announcement.To keep things more simply, this wasn't quite the "shock" that parts of the bond market were hoping for. And that matters because the Treasury is fighting up against much bigger macro forces in play at the moment.Inflation risks are rising again as oil prices hit $100, fiscal deficits remain substantial, and government borrowing needs remain enormous. All of this continues to lead investors to increasingly demand greater compensation for owning longer-duration debt.What does the buyback mean for Treasury yields?I wouldn't discount the potential for it to help improve liquidity and provide some technical support to longer-dated Treasuries. However, $6 billion is but a drop in a bucket when compared with the scale of the broader Treasury market and cannot fundamentally erase inflation or fiscal risk.That makes the buyback operation worth watching, but I wouldn't view it as a significant turning point for yields by itself.If anything else, the reaction since yesterday reinforces the bigger and more prominent message from the bond market. And that is investors will still want higher yields i.e. to be paid more to hold long-term government debt in this market and economic landscape.Until that changes, Treasury buybacks may only help to slow the pressure but they are unlikely to reverse the broader tectonic shift. This article was written by Justin Low at investinglive.com.