Ok, but is he likely to get them either way? If they are likely to have a breakout soon, you want to stop the bleeding and have time to make the rest of Ukraine a harder nut to crack. If we can even get them to negotiate at that point. Do you think Ukraine can hold the line? If not, why continue to throw their lives away? You can call a truce and regroup.
If we are being real, if they want Moldova and Transnistria, there isn't anything we could do about it short of going to war with Russia over them. I wouldn't want to do that, would you? Poland, Finland, and the Baltics are NATO members. That is the red line. If Russia entered those countries I would support actively fighting them. It sucks for the countries that aren't under the NATO umbrella but I don't think a massive war with a potential nuclear exchange is worth it for Moldova.
I am sure they would prefer to see Russia fought in Ukraine as opposed to their countries. I think the Russians would calculate our potential response when assessing whether an attack on those countries is worthwhile. I think if they did attack and we did an immediate and overwhelming conventional response against their forces, they would pull back.
We can't protect everyone, everywhere and we don't have an unlimited amount of material and treasure to send around the world to bleed our opponents. Decisions are going to have to be made because our allies haven't kept up their end of the bargain in Europe and we face a larger threat in the Pacific.