If it's all fin tube baseboard,
Don't worry about it a bit. Faster is better in the boiler, too. Same reasons.
Baseboard comes above the dew point (near 130°) of the gasses pretty fast, then things dry out and get better.
That's acceptable, and how it's done today. Cast Iron radiation is a different story, because of the lower operating temperature and the higher volume of water it contains. A system bypass at the boiler can be used to blend supply water with the return to the boiler and bump up the return temperature.
A REAL high water volume system would possibly need more flow than you want through the boiler at low temps, so you might build a boiler bypass to keep some of the pumped system flow out of the boiler and at low temps.
The hotter boiler water could blend with this bypassing water and keep the system temperatures where they need to be. That's how the primitive Levittown radiant systems were mixed, using a tankless coil boiler. Most of the water bypassed around the boiler and back into the floor.
Watch that the return water to the boiler gets above 130° in the first few minutes of a run cycle, and you'll be OK.