Affiliate Marketing Secrets

A library 15-20 minutes down the highway from us advertised a couple of storytimes this year. One toddler-friendly deal, parents stay, no registration; one for ages 4 and up, ‘parents are welcome to use this time to run errands,’ said the leaflet. Registration req’d, 45min, story, song, small craft.
I registered and brought my 4yo. A brisk lady was busy shooing the kids (3 others?) off into a separate room closed off from the rest of the library. We followed. I was asked to leave, without any lead-up or explanation or ‘Well, we don’t usually allow the parents to stay but you could take a seat there’ or anything, just: no parents.
I was not into leaving my kid with an unknown, unsupervised individual, and she had absolutely no interest in staying. We went home.
The room they’re using is a large rectangular thing with a rug &c at one end and a bunch of random chairs at the other; that parents couldn’t occupy the chairs and make sure their kids were happy and make sure the entertainment &c was something worth driving there for was, I thought, bizarre.
My instinct is to write a polite letter to the library telling them their policy is nutty. But. Is this at all common? Have you ever seen a library that kicks out the parents for a storytime? What would you say?
I don’t know how useful a letter might be as the beat-it-Mummy lady is the children’s librarian (!) and, I would assume, highly unlikely to renounce her storytime duties, and she was clearly not an empathetic caregiver of the sort I’m ever going to want to entertain my kid even if I’m ten feet away. OTOH our closer library, which is affiliated with this one, has a WONDERFUL storytime lady, and I almost want to say “Mrs Library #2 should consider attending storytime with Mrs Library #1 to see how it can work with parents in the room, etc” and generally hint that more training is req’d…
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