That is def an easy way to share a customized product where you can change even more than just the template text but I have my reservations about it because …
Here’s the URL to Highton’s product as published: (Hot link)
https://www.zazzle.com/surprised_golden_globe_fish_i_dont_remember_poker_chips-256253408166544020
Here’s the URL to the product where I used his URL parameter method to change the template text: (Hot link)
https://www.zazzle.com/surprised_golden_globe_fish_i_dont_remember_poker_chips-256253408166544020?t_text1_txt=URL%20parameter&t_text2_txt=%22trick%22%20method
Both links include the product ID number (PID) and if you follow the link to the product page, you can scroll down to “Other Info” and see the PID there as well as creation date.
Here’s the URL generated when I personalize the product and then use the Share icon on the product page: (Hot link)
https://www.zazzle.com/pd/spp/pt-chiplab_pokerchip?dz=f15f5389-df09-4b62-8ab5-1dc5fa6fffd1&clone=true&pending=true&style=composite&edgestyle=striped&edgecolor=orange&design.areas=%5Bchiplab_pokerchipnew_40mm_front%2Cchiplab_pokerchipnew_40mm_back_back%5D&social=true&view=113305378735917986&rf=238499276722080691
It does not include the PID and it starts off the same way all create-your-own blanks start off (/pd/spp/pt-) and if you follow the link it actually shows Create Your Own as page title in browser tab:

And once on the page, if you scroll down there is no “Other Info” section, the product has no PID (or creation date).
Given the lack of a PID and that the URL has a “pending=true” parameter in it, that leads me to think these modified versions are not treated as an actual existing product when shared like this. We already know that if a designer modifies their own published product, the result is treated as a personal creation and therefor no sales stats or royalties are earned on it unless you actually publish that version. You can get around that by going in anonymously, customizing your product, and then not signing in until you are prompted to on the payment page. That makes you the same as any random shopper clicking on your published product and customizing it. This is getting really confusing but, if you customize your product and share the link to that version, it seems like the same thing, that you’re creating a personal product you wouldn’t get any credit for (though you could still earn a referral on it) because it’s not considered a published product.
So, I don’t know. It seems like that Share button is there more for regular customers not worried about sales & royalties to their share customized designs for feedback before ordering, but for the designer it might have the unintended consequence of making your product a personal not-published one. Again, I don’t know , just thinking out loud here as to why this method of sharing a customized product gives me pause.