Granted, it appears that passengers are now just being denied boarding and no longer being removed en route, but, in my opinion at least, this seems to me to indicate that standees are not being carried. But you are correct, I have no way of knowing for sure that standees are being permitted now and that loads are now exceeding even standee capacity, and I do concede that possibility, but the available evidence suggests that that situation is not what is occurring.
So, you've never been on these trains or been up to the platforms or seen it first hand? You're just going by the headlines?
What you're leaving out is the difference between the SPG shuttles and unreserved trains as an example. If my understanding of them is correct, the Surfliners are unreserved. As such, that train will just load and load until there is no more room. At that point, they may say "No mas."
The SPG shuttles are reserved on the Amtrak side. As such, you can SEE how many passengers you're expecting. If you're on a 2 car train and you see 82 SCHEDULED passengers boarding at Hartford (as an example) and you're already close to capacity as you approach the station, it is easy to see how many people you can safely stand, while leaving room making sure there is room for people to stand, load and unload at the next stops.
As such, it would be easy to say to anyone else "hey there isn't room for all of you to board safely."
Crews have ALWAYS had the right (and some have exercised it while others have not) to stop taking on passengers if the overflow is creating an unsafe condition. This did happen with a disabled regional around some holiday (it all blurs together at this point but TWROPR has the details.)
Long story short, the Amtrak to somewhere south of DC broke down. They transferred passengers to another regional. The initial preference was for people going south of DC since the new regional would now go south. However, it was packed which created standing conditions. Not a problem but eventually the crew stated they had no more room to handle more standee safely. So, the train left without taking on more passengers. Years ago, they would have stuffed the bathrooms, the vestibules and put 6 people to work behind the cafe counter! ^_^
This is no longer the case. They rest of the passengers waited to transfer to the next train...which had the same problem. Eventually, they hijacked a commuter train, put the rest of the passengers and just held the other train in WAS for connecting passengers arriving on the commuter set.