If the assets that are swapped were in fact worth what the swap line values them at, there would be no need for a swap line since the assets could be lent out in the open market. While you’re technically correct that it’s not QE, since the fed reserve is not directly purchasing assets, it has a similar effect on international markets. Foreign central banks purchase or lend USD to their local banks for assets which can’t be used as good collateral (meaning counterparties don’t believe the market has enough liquidity and/or the assets are valued under par) then these central banks, if they run low on USD, swap their own currency for USD through the swap lines.

The net result is USD flows out of the Federal Reserve and into foreign bank reserves, while illiquid and/or under par assets flow into foreign central banks while foreign currency flows into the federal reserve.

So it’s not really correct to say it isn’t like QE at all since in both types of stimulus new USD is issued by the federal reserve in exchange for assets. The difference is in the terms, counterparties, and types of assets.