Rulings
Q1: Does this card's digivolution requirement where it can digivolve from a Tamer mean that the Tamer that will become a digivolution card is treated as a Digimon when it digivolves?
No, it digivolves from the Tamer as-is.
Q2: When a Tamer would digivolve using this card's digivolution requirement, is it considered a Digimon that would digivolve?
No, it isn't considered a Digimon that would digivolve. When a Tamer would digivolve using this card's digivolution requirement, "when a Digimon would digivolve" effects don't trigger.
Q3: When a Tamer digivolves using this card's digivolution requirement, is it considered a Digimon that digivolves?
No, it isn't considered a Digimon that digivolves. When a Tamer digivolves using this card's digivolution requirement, "when a Digimon digivolves" effects don't trigger.
Data Sources
Lv.4 Gigasmon BT18-014 C Hybrid | Variable | Mineral [Digivolve] [Grumblemon]: Cost 1 [On Play] [When Digivolving] 1 of your Digimon gains <Rush> for the turn. --- Inherited: [When Attacking] [Once Per Turn] Delete 1 of your opponent's Digimon with 3000 DP or less.
Lv.4 Gigasmon BT18-014 C Hybrid | Variable | Mineral [Digivolve] [Grumblemon]: Cost 1 [On Play] [When Digivolving] 1 of your Digimon gains <Rush> for the turn. --- Inherited: [When Attacking] [Once Per Turn] Delete 1 of your opponent's Digimon with 3000 DP or less.
Lv.4 Gigasmon BT18-014 C Hybrid | Variable | Mineral [Digivolve] [Grumblemon]: Cost 1 [On Play] [When Digivolving] 1 of your Digimon gains <Rush> for the turn. --- Inherited: [When Attacking] [Once Per Turn] Delete 1 of your opponent's Digimon with 3000 DP or less.
Lv.4 ギガスモン BT18-014 C ハイブリッド体 | ヴァリアブル種 | 鉱物型 「グロットモン」:コスト1 【登場時】【進化時】ターン終了まで、自分のデジモン1体は≪速攻≫を得る。 --- Inherited: 【アタック時】[ターンに1回]DP3000以下の相手のデジモン1体を消滅させる。