Either the returnees directly threaten the country’s stability, or they are a useless burden on the economy; criminals and the like. Thus, the parent country doesn’t want them back. However, stopping legitimate visas from being issued is not a threat or a punishment to the parent country. Most likely, they couldn’t care less. However, the threat of cutting off aid or even sanctions against their products, that’s something they will listen to and react to. Hit them in the wallet, not with some bureaucratic paperwork snafu that doesn’t even effect “the government.”
Some countries just have a policy of not taking back their citizens that are caught here illegally. To my knowledge no other President has ever done anything about it. That is what is different.
Some posters here say “not enough!” without knowing what a big deal this is. Who else has ran for President in the last 30 years or more would have done this?