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It's a choice. Historiclly it was common to learn ARP as soon as you got a packet. As everyting what you need is in the SYN packet as soon as it arrives there is no point to ask for it it return a SYN/ACK packet.
Historically this make a lot of send if you have a lot of systems in 1 collision domain. But times have changed and so is the size of the average collision domain. So now you (sometimes) see both ends do ARP request for just a single TCP connection.
I understand this migh look akward but that is the way I have seen ARP packet change over the years.
