Actually, 1st focal reticles go up in size at higher power settings, though always at the same rate as the target is magnified.
All the Euro manufacturers offer first focal plane reticles in some models, but pretty much all of them now offer second focal reticles as well. All 1" tube scopes I can think of from all manufacturers use second focal plane reticles. 30mm and larger tube scopes can have either.
First focal plane is better for ranging reticles, where you can range distant targets on any power setting, since the reticle always subtends the same amount on the target due to the fact the target and reticle are both on the same focal plane (both are magnified at the same time and by the same amount as magnification is changed). The reticle appears to get larger as magnification is increased, but it always changes size in direct proportion to the target image. Theoretically, the point of impact cannot shift with a first focal plane reticle, which can occur with some second focal plane scopes. FFP reticles can be more visible in low light as power is dialed up. The opposite is true at low power, however.
Second focal plane reticles are better for long range precision shooting of small targets since the crosshairs actually subtend progressively less of the target as magnification is increased (the target is magnified but the reticle isn't). SFP reticles are usually more visible in low light at low magnification settings. SFP ranging type reticles (mil- or MOA-based) are calibrated for only one magnification setting (usually the highest) math-free, since the reticle doesn't remain proportionally the same size as the target image as the power setting changes.
This topic has been discussed at length here. If you do a search, you
will find plenty of discussion on the merits of both reticle locations.
Both have advantages and disadvantages.