Since December, Facebook, Instagram, Kick, Reddit, Snapchat, Threads, TikTok, Twitch, X and YouTube have all been required to take steps to prevent young Australians accessing their platforms.
The world-first ban, which stipulates users must be 16 or older to create or hold social media accounts, made international headlines in December.
Appearing before Senate estimates on Wednesday, eSafety Commissioner Julie Inman Grant said the watchdog had seen "some improvements" in industry compliance in recent months.
But whether they were meeting their legal obligations remained to be determined, she said.
"We have not yet reached a final determination on whether platforms are taking reasonable steps, which is the high standard we must prove under the legislation," she said.
Under the Online Safety Act, platform providers are required to take "reasonable steps" to prevent children under the age of 16 from having accounts.
While the watchdog has not yet undertaken any enforcement actions in relation to the ban, Ms Inman Grant cited a number of examples of platforms changing their behaviour.
Companies have tightened their age verification systems, restricted suspected underage accounts, and removed barriers making it harder for parents to report children's accounts, Ms Inman Grant said.
She pointed to one platform which had reversed its practice of allowing users an average of 24 attempts each day to use its face recognition service to verify their age.
"It's giving them an opportunity to again jailbreak or circumvent and spoof the age assurance process," Ms Inman Grant said.
While not specifically related to the under-16 ban, Ms Inman Grant pointed to a recent enforcement action against Elon Musk's X Corp as evidence of the watchdog's authority.
The social media giant was fined $650,000 after the Federal Court found it failed to provide information to the eSafety Commissioner about the steps it was taking to tackle online child abuse material.
It was the result of a years-long legal process and resulted in X Corp admitting liability and being ordered to pay an additional $100,000 in legal costs.
"This is one of the few successful actions brought against X Corp by any regulator globally," Ms Inman Grant said.
"Such outcomes are hard-won, and they demonstrate that careful, methodical enforcement, with a substantial evidence base, delivers results."
The commissioner also disclosed fresh enforcement actions against two AI "nudify" services accused of generating exploitative deepfake imagery.
One of the platforms was attracting as many as 100,000 Australian visits a month, while the other received about half as many, Ms Inman Grant said.
