True or not, the triple soft serve (500 yen) does a good job with leveraging the nutty soy qualities of the bean but for a stronger matcha kick and a creamier mouthfeel, I prefer the one from Cha no Ikedaya (below), a shop which has been around in Shinjuku station area for more than 70 years.
In fact, the latter focuses less on their sweets as their main business is focused on the retail of tea leaves, coffee and seaweed. This is a highly convenient place to stock up green tea from regions all over Japan as there is so many variety to choose from. You can even fill up your mineral bottle with their green tea with just a small charge.
From the retail side, there are also assorted matcha snacks that are supplied from different sources. The best way to kill all birds with one stone is to get their matcha/houjicha soft serve and topped with any extra ingredients you prefer.
That said, Mame Torou isn't a shop that deals only with soy bean. This tofu cheesecake anmitsu, for example, is an amalgation of different beans; soy, tora Mame, uguisu Mame, azuki.
It is also a value-for-money choice if you want to try everything (i.e tofu cheesecake, two flavors of soft serve of your choice, kuromitsu, assorted sweet beans). That said, I think it's sufficient to try once as this is decent but not over-the-top delicious.
Anyway, there are already green tea shops in Shinjuku area for matcha lovers to hunt down so don't be in a rush. Take your time and savour them one by one.
Mame Torou 豆とろう
Nishi-shinjuku 1-1-2 新宿メトロ食堂街 B1F
Cha No Ikeda Ya 茶の池田屋
Odakyu Ace South
Nearest Station: Shinjuku