Hello JGeoff. The newer formulation of Trellegy does have double the amount of Fluticasone Fuorate, an inhalable steroid (ICS). The use of triple therapy meds has only recently been advanced as an improved treatment for Severe Asthma too. By including a LAMA ingredient, this has slowly proven more effective as a single Asthma treatment. But that ingredient also falls in a class of medications known as Anticholinergics - with several cautions and drug interactions of its own.
The increased steroid dosage should help better with reducing airway inflammation which causes symptoms like wheezing and SoB. But along with that comes the usual risks of using more inhaled steroids - such as frequent throat infections and higher chance of pneumonia.
You are correct that only the 100 mcg dosage has been approved for COPD. It is the only dosage I have ever used and it works well. I was switched from Breo (ICS + LABA) to Trelegy a few years ago. If this is your first time using any of the GSK inhaler brands, Your doctor should be able to explain to you his rationale for starting at the higher dosage.

I have Trelegy 100. i actually prefer my Symibcort. The medication was prescribed for me by my nurse practioner. she didn't even ask she just changed it. The best medication I had was Advair. it really worked. Symbicort took a little while to get used to. Now I'm on Trelegy. don't really see much difference. i'm going to ask to see my actual pulmonologist.

Many people take Trelegy and it works well for them. For me, it's the first time I've been able to take any LABA without having serious trouble breathing and it works well for me. Prior to going to Trelegy I used Advair and Combivent respimat and I do breathe better using the Trelegy. The difference in dosage is interesting and I'll admit I don't quite understand. I suspect the increased LABA is because of the effect of that bronchodilator. So yes, Trelegy does work for some people. It may not work well for you. If it doesn't work well for you and you still want to try a triple therapy, Breztri is al available.