On a Matz the rate is fixed for a period, typically five years, and then reset to market levels, while the balance is indexed to the Madad every month. Its starting rate is usually the lowest on offer, which is why it is tempting. It counts as variable under the 66.66% rule of Directive 329.
Because both the rate and the balance can rise, Matz is the hardest track to forecast. Test it against a scenario with higher rates and higher inflation. On the other hand, repaying on a reset date carries only the small operational fee, so you can leave or refinance the track at that moment without a capitalization fee.
The pitfall is the low starting rate. It is the price of taking two risks at once, and the payment you must afford is the one after the first reset, not the first one.
Example
₪400,000 in Matz over 25 years at 3% for the first 5 years has a payment of about ₪1,897 (ignoring indexation). After 5 years about ₪342,000 remains. If the rate is reset to 4.5%, the payment for the remaining 20 years is about ₪2,164, about ₪267 (14%) more, before any inflation.