Not exactly true. RBCS trimmer #2 and some older Forester presses used a "universal case holder". That is a device which expands and contracts to accept a variety of different size cartridges. They had a tightening ring that would pressure the base and hold the cases tight.
I use RCBS and Lee dies. I have found all my Lee dies do good but RCBS shell holders always fit.. A few of my Lee's have been just a little loosey-goosey and one caliber won't hold a case to remove it from the sizing die. It was replaced with an RCBS. Shell holders are inexpensive compared to other tools. By the way, RCBS has a lifetime warranty on most of their reloading equipment excepting their electronics. I believe it even covers their inertia bullet puller. Lee does not.