For those who don't know, spellpoint is a variant system where your Spell Slots (and usually Sorcery Points) are basically merged into one big pool together. This not only makes Sorc incredibly potent when it comes to specializing since they can spam a certain spell as many time as they please (until you completely empty your pool really), it pretty much fits Sorcerer flavor to a T. Want to make someone that only casts Empowered Transmuted (Lightning) Fireball? This is for you. You also can pretty much spend your SP on the fly in a similar manner with this variant rule. Many actually recommend DM to let Sorc use this system for these reasons but of course many are still reluctant against using variant rule.

Anyway due to Font of Magic, Sorc is the closest one to be able to replicate the feature. However it comes with a cap that is needing a Bonus Action for every convert. It doesn't sound like a huge cost, but if you are running heavy Quickening build it obviously clashes again each other. There are also various other good bonus action spell like Misty Step, or Spiritual Weapon (Divine Soul can get it). Also those with Telekinetic feat can not use the bonus shove action. And in cases that you need to convert spell slots to different level it would need two BA (first to SP and then SP back to spell slot).

There's also an issue with SP cap. A level 7 Sorc can only have 7 SP max (ignoring feat / magic items and other abuse). This means they can only do Quicken like thrice before running out of SP and have to spend bonus action in the subsequent turn to convert more if the battle hasn't ended yet.

In UA7, converting spell slot to SP is now pretty much at-will. This is an incredible change allowing you to abuse your metamagic to the limit without disrupting the flow. Granted converting SP into spell slot still need Bonus Action, but it is still a cut in half when it comes to action economy, and in my experience most of the time you would want to prioritize spell slot -> SP anyway.

So yeah, small change on paper but is actually quite incredible imo.