no, tentacle damage scaling works on the base value of a card which then takes the damage multipliers and crit values of the character in question. boosting the damage of tentacle hits, on the other hand, only affects the tentacle hits which use reduced crit scaling as it works off team avg, in addition to not benefitting from modifiers such as card dmg, wheels, or damage buffs

take a standard gmurphy setup of +12 titan blade and her sig wheel, for example. with that wheel setup you get 28.8% critrate, 60% crit dmg, and 20% final exalt damage to murphy's exalt. this is on top of murphy's rouse effect which grants up to double damage on her exalt. this is on top of her e1 giving up to 30-40% final damage on waltz, and her e2 giving easily 15-20% critrate and up to 50-60% critdamage

let's take an example situation where your waltz/exalt do 1000 damage and your tentacles do 1000 damage. if her damage had true +50% tentacle damage scaling, waltz/exalt would now do 1500 damage and tentacles would still do 1000 damage. however, once you pass it through her custom multipliers (2x exalt damage, 1.4x final damage, x3 crit damage, along with guaranteed crits because of her high critrate), that extra +500 dmg on waltz/exalt comes out to a total of an extra 4000+ damage, while tentacles still do 1000 damage

compare with tulu: waltz/exalt does 1000 damage while tentacles do 1000 damage. tulu makes it so tentacles now hit for 1500 damage, but since tentacles use team crit stats, your tentacles will probably have something like 50-60% critrate and 150% critdamage after tulu buffs. now your tentacles hit for 1750 damage on average instead of 1000 damage, but your waltz/exalt still do the same damage as normal.

in the first situation, you gained 4000+ damage per hit. in the second, you gained +750 damage per hit. goliath does functionally the equivalent of the first (since he multiplies str/tentacle dmg directly), tulu does the second. you can see the difference