Lots of misinformation about TCA here, let me see if i can clarafy:
TCA produces 1 LI unit per a time interval. This time interval is dynamic, and changes all the time.
The time interval formula is as follows:
Time to produce next unit = 30 seconds (base time) + .5*(number of barracks units)
This means the base time (assuming no barracks units of yours' on the field) is 30 seconds, plus 1/2 second for every barracks unit on the feild. This is the simulated ramping cost, just changed into time.
I highly doubt your TCA produced 4 units from medieval to enlightenment, unless you already had a bucketload of barracks units and advanced very quickly. The number of TCA units you see when you click the TCA (on the display panel it says how many units created by TCA are on the field) you must remember that this number goes down when your TCA units are killed. If you are basing you 4 units on this number then it's likely some of your other TCA units were killed.
It's also posible that you clicked light infantry and hit "home" at some point which sent all your LI (including those from TCA) to the front, and started the count over again.
Even if you had 50 barracks units (which is considerably more than you normally see in medieval-enlightenment), that would still be 1 unit per 55 seconds. So unless you aged up 2 ages in <4 minutes, your claim does not compute.