You make some good points.
I think there are three things which - maybe by coincidence - align to give a suspicious appearance.
The central question is whether Price received insider information from Collins (a definite insider), or whether the purchase was made on the strength of Price's own research.
Price claims innocence. But the transaction certainly has a whiff about it.
“[Collins] was reportedly overheard just last week off the House floor bragging about how he had made people millionaires from a stock tip. Congressman Price, in our meeting, you informed me you made these purchases based on conversations with Representative Collins."
Second, it seems he was front-running the legislation. He claims it was inadvertent.
Third, that's a privileged trade. Hot IPOs are the underpriced candy of investing. He was given a great big sugary rock of it. He surely knew he was getting a fabulous advantage over regular investors, in spite of the denial. But that part of things is probably between him and Morgan Stanley rather than him and the law.
So there are three things here that give grounds for questioning. But indeed, it may have been a coincidence. I don't know.