Not true for many reasons.
1) Lower level upgrades of all LTBs are great investments (very low ROI period) as save upgrades.
2) Pagoda, West Side Gems, and No Interest Savings are great investments into the middle levels.
3) When you get to a very high IPH, NC isn't that great anymore, the upgrade time is so long that it actually works as a save upgrade. And when you have too much cash on hand, the higher level LTB upgrades start becoming better investments on a dIPH/t metric, which is more important if you have an abundance of cash.
Save upgrade = any upgrade that at the end of the upgrade you have more money on hand then when you started the upgrade.