The fact that Abp Garcia-Siller has not made frequent, or any, use of this canon previously proves nothing about the merits of this case. Catholic clergy are moved regularly for pastoral reasons; this formal process represents a last resort when the man in question cannot be otherwise motivated. This is not the typical frame of mind of a Catholic priest, who has been dependent for a lifetime on his bishop's goodwill. You often comment on the difference between Catholic formation and that of other clergy, and we see here an example of the results. Fr Phillips is still the man who upped stakes and left Rhode Island for Texas. Still the man who did an abrupt about-face when he discovered that Msgr Steenson had plans for the parish which did not include him. He is forcing Abp G-S to use a canonical process which I would imagine is very seldom undertaken in the Church. As you point out, canon 1742 is not the one used when a priest has lost collection money at the racetrack, performed a same-sex wedding, or had an affair with the parish secretary. It is vague and I imagine that "ineffectiveness" is hard to prove. If this has been dragging on since last summer it is because Abp G-S has tried every other informal means to twist Fr Phillips' arm, to no avail.An issue I've noted before is that in many dioceses, Catholic pastors rotate on six- or 12-year cycles. Fr Phillips has stayed at OLA since its founding. For him to feel entitled to stay there until his retirement, or for the parish to expect it (and expect to get a successor he nominates, if this is the case) doesn't seem reasonable.
The idea that incumbents in any job must rotate out is a basic feature in the US military. It is common in corporations, at least in lower and middle levels. Financial institutions require that employees take vacations for two consecutive weeks each year on the assumption that frauds can't be maintained for that length of time. The idea that someone is entitled to stay in a position indefinitely is not good practice in general.