Note - not running hor, dont confuse. Of coz got other factors as well (some of which marginal), but compared to running it's probably slightly more important.
A lot has been said regarding smartwatches accuracy of VO2max values, but lets be real man, if the trend is up, it is up esp if sustained over months/years. No horse run one lah.
There is a ceiling and it's largely determined by genetics with a +15 to 30% of that ceiling as trainable, but it is still not a low ceiling. If you are starting off very low from a semi untrained state at say 25-30 ml/kg/min, that ceiling is still so bloody high.
But remember, take it easy, even for me i find it to be really hard. These sessions are surgical strikes and for older folks need more than 3 or more days for recovery (can do your Z2 or even parts Z1 between them)
Anyway i noticed this channel really likes micro intervals. lol

Pucking horrible training (i started 2 weeks ago) the ending intervals need to spew vulgarities to mentally keep going one, but can try lah. But i think if it really is too hard, maybe it is time to exercise cut or add even more recovery time and slowly progess up in latter sessions (too hard too soon, age dependent?)
One example listed 2 years claimed literally zero improvement with regular intervals but within 6 weeks of this +7% 20 min power liao.

No harm trying if can tahan.