When the game starts, for the first 25 minutes queen is restricted to certain areas for hive core and ovi - primarily caves on most maps. (mechanic from Better Control of Weeding and Areas - Landing Zone edition. by Nanu308 · Pull Request #7363 · cmss13-devs/cmss13 · GitHub).
The new PR makes it where yes a queen during the first 20 mins of play if she is in the area w/ the hive core or within 10 tiles from it (so it also handles a core on an area border) she is mature and refreshes a 1 minute timer. If she leaves that range the timer counts down. If she takes damage while the timer is running, it’ll extend the timer by 15s up to its maximum of 1 minute. If the timer expires, she loses maturity. Normal maturity timer is still running.
The only thing I really feel like is up in the air is if 1 minute is too long for queen to feel like she can assault survivors and keep maturity long enough to assault them. The intention is just for her to be mature when defending her hive and a small window to give chase or to keep it when being attacked.