I've always blown up balloons by mouth. It's faster than a pump and gives more control. But I've been through some health issues and I'm now using my Filbert pump.

I've noticed that the Filbert blown balloons are different from mouth blown. I think it is the warm breath. Filbert pumped balloons seem much more tight and pop more easily even when I stretch the balloon before pumping and burp the balloon after.

Just curious if anyone else noticed this.

Yes - This observation is also presemt with "normal" hand pumps

You are correct
Give the balloon a pre-stretch between your fingers, this will "activate" the latex, and minimise the tightness
Also you can give the inflated balloon another stretch to encourage malleability

I've been using a Filbert Pump for years - never had a problem with it, just 'burp' the balloon a wee bit after you inflate. This should easily cure any issues.
Balloons by mouth - never a good plan for one's long term health.

Does anyone have the website for the Filbert Pump?

https://www.filbertpump.com/