Oh dear...
Because (big sigh), if you read the OP (!!), the baroness was on the pavement, because the bus driver did not deploy the ramp for her to get on board. From this position, a person can see the driver, and the wheelchair space. What they cannot see is who the owner of the buggy is, because they are likely sat down towards the back, out of sight from someone in a seated position on the pavement.
It is possible to tell as a bus pulls up whether it is "full" or "half empty" by looking for empty seats or the presence of standees.
Well, quite. What if the baroness didn't know either, hm? And that's why they truthfully say they can't see the parent?
Even if the driver doesn't know who it belongs to, he, in law, as I have explained, should take steps to ensure that the buggy owner modifies their behaviour. The law says he could make an announcement, or refuse to move the bus forward until the offending buggy is gone. He must take reasonable steps to ensure the disabled person can complete their journey. Sometimes, he won't be able to force someone to behave, and must deny the wheelchair user after some effort - but that's wholly different to saying "the ramp's not coming down, get the next bus, I'm not asking the owner to move it, bye".
I am not sure why you are so content with repeatedly blaming the baroness or casting aspersions on her version of events with no evidence to back that up other than your own prejudices. There isn't any evidence at all to suggest she is being untruthful, and for someone who claims not to use buses, you are making a lot of assumptions based on what seems to be very little practical experience.