Current source or current mirror?
Your question is very specific, but I think what you're getting at is a more general concept.

In typical general-use simulators, "current sources" are modeled as ideal. An ideal current source will provide the exact amount of current requested regardless of external influences. It will adjust its voltage instantaneously as needed to continue to provide that exact current flow no matter what.

Realistic? Not at all. Any real current source will always be influenced by external forces. A sudden step change in load resistance, for example, may cause the current source to spike up or down. Or what if the load becomes open circuit? The realistic current source may attempt to raise its voltage until it fails catastrophically (or simply powers down if it's smart enough).

Using a current mirror as a realistic current source is one of many ways to model a more realistic current source. Current mirrors are very simply to build - just two transistors and a resistor - which is probably why this person suggested using them. But current mirrors exhibit properties that may not be adequate for your simulation. Sometimes an ideal current source will work just fine. Other times a more sophisticated model is necessary. As with all things electronics, it depends on your application.