Any reputable, knowledgeable detailer or tint installer can tint your sunroof. A tinted sunroof is no more prone to breakage than a non-tinted roof. It just isn't - in fact tint film can reduce the likelihood of glass particles falling into the cockpit in the event it does shatter. Tempered glass (the more common material used in sunroof manufacturing)
can "spontaneously" shatter, reported in numerous blogs and anecdotal stories, and in fact BMW and MB have been involved in consumer lawsuits as a result. The fact is that the manufacturing process itself in tempered glass production can make it prone to this - primarily because of the necessary inclusion of nickel sulfide (NiS), an impurity -
A Small Speck Causes Big Problems: Identifying Spontaneous Glass Fracture. Manufacturers mitigate this by heat-soaking the glass post-production, but a microscopic nidus of an impurity can cause tempered glass to shatter spontaneously, and it's luck of the draw - zero to do with tinting.
And a primer on tempered glass - it's glass toughened by heat (or less often chemical) tempering, placing the internal glass structure under tremendous strain, making it more resistant to breakage, but when it does break causing it to break into thousands of small, less dangerous dull bits -
How is tempered glass made?. That tension-structure internal to the glass can make it paradoxically more prone to shatter with tiny internal or external imperfections - even small chips or dings during or subsequent to manufacturing (or even caused by sloppy or inexperienced detailers applying tint). As a secondary note, tempered glass can withstand a temperature differential of almost 500F - it's not going to "overheat" with exposure to sunlight, unless you live on Mercury.
That said, the sunroof in the iX is not single-pane tempered glass - it's PDLC (Polymer Dispersed Liquid Crystal) glass, used for years in the construction industry for windows and walls -
https://www.sciencedirect.com/topics/chemistry/polymer-dispersed-liquid-crystal. More accurately, a layer of PDLC sandwiched between two layers of glass, so actually closer to laminated glass than tempered. The in-use durability remains to be seen, and there have been reported sunroof fractures in the iX, but likely it's at least as tough as standard tempered glass, and consequently as vulnerable to shattering with chips, nicks or dings. Time will tell. But no more vulnerable to breakage than standard tempered glass as a result of tinting it. And as a disclaimer, I'm not telling anyone to tint - or not - their iX sunroof. Mine is - 50% - and it reduces the internal temperature and UV transmission considerably, and I would do it again (in fact I am on spouse's iX), but "you do you" is still a wise adage. PSA out.